Spectroscopy

The atomic fluorescence spectroscopy (AFS) method is one of the luminescent methods. The analytical signal is the intensity of radiation belonging to the optical range and emitted by excited atoms. Atoms are excited under the influence of an external source of radiation. The fraction of excited atoms and, therefore, the luminescence intensity I are determined primarily by the intensity of this source I0 in accordance with the approximate relation

where k is the absorption coefficient; l is the length of the optical path; - fluorescence quantum yield; - concentration of luminescent particles (atoms of the element being determined).

As a rule, quantum yields decrease greatly with increasing temperature. Due to the fact that atomic fluorescence analysis requires high temperature, the values ​​for free atoms are extremely small. Therefore, in APS, the use of radiation sources as powerful as possible is crucial. As such, high-intensity discharge lamps (with a hollow cathode or electrodeless), as well as lasers with tunable frequencies are used.

Now the AFS method is being developed mainly in the laser version (laser atomic fluorescence spectroscopy, LAFS).

The use of lasers has dramatically increased the sensitivity of the method. The main advantage of the APS method is its high selectivity (the highest among optical atomic spectroscopy methods), due to the simplicity of the atomic fluorescence spectra and the absence of overlap of the spectral lines of various elements.

X-ray spectroscopy

Interaction of X-rays with matter. When X-ray radiation passes through a sample, it is attenuated due to absorption, as well as elastic and inelastic (Compton) scattering by electrons of atoms of the solid. The main contribution to the attenuation of X-ray radiation comes from its absorption. With increasing wavelength (decreasing energy) of the X-ray quantum, the mass absorption coefficient gradually increases. When a certain wavelength of the absorption edge is reached, the mass attenuation coefficient decreases sharply. This process is repeated many times over the entire wavelength range (up to vacuum ultraviolet).

X-ray spectrum - distribution of the intensity of X-ray radiation emitted by a sample (REA, XRF) or transmitted through the sample (RAA), according to energies (or wavelengths). The X-ray spectrum contains a small number of spectral lines (emission spectrum) or absorption “jumps” (absorption spectrum). The background signal of the emission spectrum is formed by X-ray quanta inelastically scattered by electrons of atoms of a solid body. X-ray emission occurs during electronic transitions between the internal levels of atoms. The relative “simplicity” of the X-ray spectrum is due to the limited number of possible electronic transitions.

Sources of spectrum excitation. An X-ray tube is used to excite the spectrum in REA, RAA and XRF.

Its working element is a pair of evacuated electrodes - a thermionic cathode and a cooled anode made of refractory material with good thermal conductivity (W, Mo, Cu, etc.). The sample to be analyzed is placed directly on the anode of the X-ray tube. As a result of electron bombardment, X-rays are emitted from the surface of the sample. To excite the spectrum in RAA and XRF, primary X-ray radiation generated by an X-ray tube is used. In RAA, the degree of monochromaticity of X-ray radiation should be higher.

A type of REA is electron probe X-ray spectral microanalysis (EPMA). In it, to excite the X-ray spectrum, a monoenergetic electron beam (analysis at a “point”) or a scanning electron beam - raster (analysis of a surface area) is used. Thus, EPMA is a local analysis method. The excitation source is an electron gun. It consists of a field- or thermionic cathode and a system of accelerating and focusing electrostatic or magnetic lenses operating under high vacuum conditions.

X-ray emission analysis.

Hardware design of the method. The main components of any X-ray emission spectrometer (X-ray emission spectrometer) are the spectrum excitation source, the entrance slit (or collimator), the sample mounting and input device, the output slit, and a general system for analyzing and detecting X-ray emission. Depending on the operating principle of the last unit, a distinction is made between wave dispersion spectrometers (WDS) and energy dispersion spectrometers (EDS). In SVD, an analyzer crystal is used to disperse X-rays, and a proportional or scintillation detector is used to detect them. In the SED, the functions of analyzer and detector are combined by a cooled semiconductor detector (SSD). Its advantages include a larger signal and shorter duration of the signal. SVD has a higher spectral resolution. This allows you to confidently distinguish lines with similar wavelengths in the spectrum. However, SED has a higher aperture ratio. This leads to an increase in the intensity of the measured spectral lines.

Possibilities of the method and its application. The REA method allows for simultaneous multi-element qualitative and quantitative analysis solid samples. Using SED it is possible to determine elements from Na to U, and using SVD - from B to U. The lowest values ​​of determined contents are achieved in the case of heavy elements in light matrices. The EPMA method is used for local analysis of the surface layers of samples containing microscopic heterophases (including for the analysis of high-tech materials).

X-ray fluorescence analysis

Hardware design of the method. The design of the XRF spectrometer and X-ray spectrometer are similar. Vacuum XRF spectrometers can work with long-wave X-rays and detect light elements. For local analysis of the surface of a solid body, modern XRF spectrometers based on capillary X-ray optics are used.

Sample preparation The accuracy of quantitative XRF is determined by the correctness and reliability of sample preparation. Solutions, powders, metals and alloys can be examined. The main requirement for a sample is that the intensity of the analytical line of the element being determined depends on its concentration. The influence of all other factors must be excluded or stabilized.

Possibilities of the method and its application. The XRF method allows for non-destructive simultaneous multi-element qualitative and quantitative analysis of solid and liquid samples. The lowest values ​​of determined contents are achieved in the case of heavy elements in light matrices. The XRF method is used for the analysis of metals, alloys, rocks, environmental monitoring of soils, bottom sediments.

X-ray absorption analysis.

Hardware design of the method. The main components of an RA spectrometer are an X-ray source, a monochromator, a device for fastening and introducing a sample, and a detector.

Possibilities of the method and its application. The RAA method has not found wide application due to its low selectivity, but in cases where a matrix of light elements contains only one detectable element of large atomic mass, the use of this method is quite advisable. RAA is used for serial determination of heavy elements in samples of constant composition, for example lead in gasoline, etc.

1. X-ray spectroscopy

X-ray spectroscopy, obtaining X-ray emission and absorption spectra and their application to the study of the electronic energy structure of atoms, molecules and solids. X-ray spectroscopy also includes X-ray electron spectroscopy, i.e. spectroscopy of X-ray photo- and Auger electrons, study of the dependence of the intensity of the bremsstrahlung and characteristic spectra on the voltage on the X-ray tube (isochromat method), spectroscopy of excitation potentials.

X-ray emission spectra are obtained either by bombarding the substance under study, which serves as a target in an X-ray tube, with accelerated electrons (primary spectra), or by irradiating the substance with primary rays (fluorescence spectra). Emission spectra are recorded by X-ray spectrometers. They are studied by the dependence of the radiation intensity on the energy of the X-ray photon. The shape and position of X-ray emission spectra provide information about the energy distribution of the density of states of valence electrons and make it possible to experimentally reveal the symmetry of their wave functions and their distribution between strongly bound localized electrons of the atom and itinerant electrons of the solid body.

X-ray absorption spectra are formed by passing a narrow portion of the bremsstrahlung spectrum through a thin layer of the substance under study. By studying the dependence of the absorption coefficient of X-ray radiation by a substance on the energy of X-ray photons, information is obtained about the energy distribution of the density of free electronic states. The spectral positions of the boundary of the absorption spectrum and the maxima of its fine structure make it possible to find the multiplicity of ion charges in compounds (it can be determined in many cases by the shifts of the main lines of the emission spectrum). X-ray spectroscopy also makes it possible to establish the symmetry of the immediate environment of an atom and to study the nature of a chemical bond. X-ray spectra, resulting from the bombardment of target atoms with high-energy heavy ions, provide information about the distribution of emitting atoms according to the multiplicity of internal ionizations. X-ray electron spectroscopy is used to determine the energy of internal levels of atoms, for chemical analysis and determination of the valence states of atoms in chemical compounds.

1. X-ray equipment. X-ray camera and x-ray tube

An X-ray camera is a device for studying or monitoring the atomic structure of a sample by recording on photographic film the pattern that appears during the diffraction of X-rays on the sample under study. An X-ray camera is used in X-ray structural analysis. The purpose of the X-ray camera is to ensure that the conditions for X-ray diffraction are met and X-ray images are obtained.

The source of radiation for an X-ray camera is an X-ray tube. X-ray cameras can be structurally different depending on the specialization of the camera (X-ray camera for studying single crystals, polycrystals; X-ray camera for obtaining small-angle X-ray images, X-ray camera for X-ray topography, etc.). All types of X-ray cameras contain a collimator, a sample installation unit, a cassette with photographic film, a mechanism for moving the sample (and sometimes cassettes). The collimator forms the working beam of primary radiation and is a system of slits (holes), which, together with the focus of the X-ray tube, determine the direction and divergence of the beam (the so-called geometry of the method). Instead of a collimator, a monochromator crystal (flat or curved) can be installed at the camera entrance. The monochromator selects X-ray radiation of certain wavelengths in the primary beam; a similar effect can be achieved by installing selectively absorbing filters in the chamber.

The sample installation unit secures it in the holder and sets its initial position relative to the primary beam. It also serves to center the sample (bringing it to the axis of rotation), and in the X-ray chamber for studying single crystals, it also serves to tilt the sample on the goniometric head (Fig. 3.4.1). If the sample has the shape of a plate, then it is fixed on adjusted guides. This eliminates the need for additional centering of the sample. In X-ray topography of large single crystal wafers, the sample holder can be translated (scanned) synchronously with the film displacement while maintaining the angular position of the sample.

Fig.3.4.1. Goniometric head: O – sample, D – arc guides for tilting the sample in two mutually perpendicular directions; MC – sample centering mechanism, which serves to place the center of the arcs in which the sample is located on the camera rotation axis

The X-ray camera cassette is used to give the photographic film the required shape and for light protection. The most common cassettes are flat and cylindrical (usually coaxial with the axis of rotation of the sample; for focusing methods, the sample is placed on the surface of the cylinder). In other X-ray cameras (eg, X-ray goniometers, X-ray topography chamber), the cassette moves or rotates synchronously with the movement of the sample. In some x-ray cameras (integrating), the cassette also moves by a small amount with each x-ray cycle. This leads to smearing of the diffraction maximum on the photographic film, averaging of the recorded radiation intensity and increases the accuracy of its measurement.

The movement of the sample and the cassette are used for different purposes. When polycrystals rotate, the number of crystallites that fall into the reflective position increases - the diffraction line on the x-ray diffraction pattern turns out to be uniformly blackened. The movement of the single crystal allows different crystallographic planes to be brought into a reflective position. In topographic methods, the movement of a sample allows one to expand the area of ​​its study. In the X-ray chamber, where the cassette moves synchronously with the sample, the mechanism for its movement is connected to the mechanism for moving the sample.

An X-ray camera makes it possible to obtain the structure of a substance both under normal conditions and at high and low temperatures, in a deep vacuum, an atmosphere of a special composition, under mechanical deformations and stress, etc. The sample holder may have devices to create the necessary temperatures, vacuum, pressure, measuring instruments and protection of camera components from unwanted influences.

X-ray cameras for studying polycrystals and single crystals are significantly different. To study polycrystals, you can use a parallel primary beam (Debye X-ray cameras: Fig. 3.4.2, a) and divergent (focusing X-ray cameras: Fig. 3.4.2, b and c). Focusing X-ray cameras have a high speed of measurements, but the X-ray images obtained with them record only a limited range of diffraction angles. In these X-ray cameras, a radioactive isotope source can serve as the source of primary radiation.

Fig.3.4.2. Basic diagrams of X-ray cameras for studying polycrystals: a – Debye chamber; b – focusing chamber with a curved monochromator crystal for studying samples “through transmission” (region of small diffraction angles); c – focusing camera for reverse photography (large diffraction angles) onto a flat cassette. The arrows show the directions of the direct and diffraction beams. O – sample; F – X-ray tube focus; M – monochromator crystal; K – cassette with photographic film F; L – trap that intercepts the unused X-ray beam; FO – focusing circle (the circle along which the diffraction maxima are located); CL – collimator; MC – sample centering mechanism

X-ray cameras for studying microcrystals are structurally different depending on their purpose. There are cameras for crystal orientation, that is, determining the direction of its crystallographic axes (Fig. 3.4.3, a). Rotation-oscillation X-ray camera for measuring crystal lattice parameters (by measuring the diffraction angle of individual reflections or the position of the main lines) and to determine the type of unit cell (Fig. 3.4.3, b).

Fig.3.4.3. Basic schemes of X-ray cameras for studying single crystals: a – chamber for studying stationary single crystals using the Laue method; b – rotation chamber.

The photographic film shows diffraction maxima located along the layer lines; when replacing rotation with vibration of the sample, the number of reflections on the layer lines is limited by the range of vibrations. Rotation of the sample is carried out using gears 1 and 2, its vibrations through kaloid 3 and lever 4; c – X-ray camera to determine the size and shape of the unit cell. O – sample, GG – goniometric head, γ – halo and axis of rotation of the goniometric head; GL – collimator; K – cassette with photographic film F; CE – cassette for shooting epigrams (reverse shooting); MD – mechanism of rotation or vibration of the sample; φ – halo and axis of vibration of the sample; δ – arc guide for tilting the axis of the goniometric head

An X-ray camera for separate registration of diffraction maxima (scanning of layer lines) is called X-ray goniometers with photo registration; topographic X-ray camera for studying lattice disturbances in nearly perfect crystals. Single crystal X-ray cameras are often equipped with a reflectance goniometer system for measuring and initial setting of cut crystals.

To study amorphous and glassy bodies, as well as solutions, X-ray cameras are used that record scattering at small diffraction angles (of the order of several arcseconds) near the primary beam; The collimators of such cameras must ensure non-divergence of the primary beam so that radiation scattered by the object under study at small angles can be isolated. To do this, they use beam convergence, extended ideal crystallographic planes, create a vacuum, etc. X-ray cameras for studying micron-sized objects are used with high-focus X-ray tubes; in this case, the sample-film distance can be significantly reduced (microcameras).

An X-ray camera is often called by the name of the author of the radiography method used in this device.

X-ray tube, an electric vacuum device that serves as a source of X-ray radiation. Such radiation occurs when electrons emitted by the cathode are decelerated and hit the anode (anti-cathode); in this case, the energy of electrons accelerated by a strong electric field in the space between the anode and cathode is partially converted into X-ray energy. The X-ray tube radiation is a superposition of bremsstrahlung X-ray radiation on the characteristic radiation of the anode substance. X-ray tubes are distinguished: by the method of obtaining a flow of electrons - with a thermionic (heated) cathode, field emission (tip) cathode, a cathode bombarded with positive ions and with a radioactive (β) source of electrons; by the method of evacuation - sealed, dismountable, by the time of radiation - continuous, pulsed; by type of anode cooling - with water, oil, air, radiation cooling; by focus size (radiation area at the anode) - macrofocal, sharp-focus; according to its shape - ring, round, line shape; according to the method of focusing electrons on the anode - with electrostatic, magnetic, electromagnetic focusing.

The X-ray tube is used in X-ray structural analysis, spectral analysis, X-ray spectroscopy, X-ray diagnostics, X-ray therapy, X-ray microscopy and microradiography.

The most widely used in all areas are sealed X-ray tubes with a thermionic cathode, a water-cooled anode, and an electrostatic electron focusing system (Fig. 3.4.4).

The thermionic cathode of an X-ray tube is a spiral or straight filament of tungsten wire, heated by electric current. The working area of ​​the anode - a metal mirror surface - is located perpendicularly or at a certain angle to the electron flow. To obtain a continuous spectrum of high-energy and high-intensity X-ray radiation, anodes made of Au and W are used; in structural analysis, X-ray tubes with anodes made of Ti, Cr, Fe, Co, Cu, Mo, Ag are used. The main characteristics of the X-ray tube are the maximum permissible accelerating voltage (1-500 kV), electron current (0.01 mA - 1 A), specific power dissipated by the anode (10 - 104 W/mm2), total power consumption (0.002 W - 60 kW).

Fig.3.4.4. X-ray tube diagram for structural analysis: 1 - metal anode cup (usually grounded); 2 – beryllium windows for X-ray emission; 3 – thermionic cathode; 4 – glass flask, isolating the anode part of the tube from the cathode; 5 – cathode terminals, to which the filament voltage is supplied, as well as high (relative to the anode) voltage; 6 – electrostatic electron focusing system; 7 – input (anti-cathode); 8 – pipes for inlet and outlet of running water cooling the inlet glass

AES is based on thermal excitation of free atoms and registration of the optical emission spectrum of excited atoms:

A + E = A* = A + hγ,

where: A – atom of the element; A* - excited atom; hγ – emitted light quantum; E is the energy absorbed by the atom.

Sources of excitation of atoms = atomizers (see earlier)

Atomic absorption spectroscopy

AAS is based on the absorption of radiation in the optical range by unexcited free atoms:

A + hγ (from internal source) = A*,

where: A – atom of the element; A* - excited atom; hγ – light quantum absorbed by the atom.

atomizers – flame, electrothermal (see earlier)

A feature of AAS is the presence in the device of external radiation sources characterized by a high degree of monochromaticity.

Radiation sources – hollow cathode lamps and electrodeless discharge lamps

Atomic X-ray spectroscopy

X-ray spectroscopy methods use X-ray radiation corresponding to a change in the energy of internal electrons.

The structures of the energy levels of internal electrons in the atomic and molecular states are close, so atomization of the sample is not required.

Since all internal orbitals in atoms are filled, transitions of internal electrons are possible only if a vacancy is previously formed due to ionization of the atom.

Ionization of an atom occurs under the influence of an external source of X-ray radiation

Classification of ARS methods

Spectroscopy of electromagnetic radiation:

X-ray emission analysis(REA);

X-ray absorption analysis(RAA);

X-ray fluorescence analysis(XRF).

Electronic:

X-ray photoelectron(XPS);

Auger electronic(ECO).

Molecular spectroscopy

Classification of methods:

Emission(does not exist) Why?

Absorption:

Spectrophotomery (in BC and UV);

IR spectroscopy.

Luminescent analysis(fluorimetry).

Turbidimetry and nephelometry.

Polarimetry.

Refractometry .

Molecular absorption spectroscopy

Molecular absorption spectroscopy is based on energy and vibrational transitions of outer (valence) electrons in molecules. Radiation from the UV and visible regions of the optical range is used - this is spectrophotometry (energy electronic transitions). Radiation from the IR region of the optical range is used - this is IR spectroscopy (vibrational transitions).

Spectrophotometry

Based on:

Bouguer-Lambert-Beer law:

The law of additivity of optical densities:

A = ε 1 l C 1 + ε 2 l C 2 +….

Analysis of colored solutions - in BC (photocolorimetry);

Analysis of solutions capable of absorbing ultraviolet light - in UV (spectrophotometry).

Answer the questions:

Basic techniques for photometric measurements

Calibration graph method.

Method of additives.

Extraction-photometric method.

Method of differential photometry.

Photometric titration.

Photometric determination consists of:

1 Converting the defined component to

light-absorbing compound.

2 Light absorption intensity measurements

(absorption) with a solution of a light-absorbing compound.

Applications of photometry

1 Substances with intense bands

absorption (ε ≥ 10 3) is determined by its own

light absorption (BC – KMnO 4, UV – phenol).

2 Substances that do not have their own

light absorption, analyzed after

photometric reactions (obtained from

wind-absorbing compounds). In n/x - reactions

complex formation, in o / x - synthesis of organic

dyes.

3 Extraction photometric methods are widely used

method. What it is? How to make the determination? Examples.

Master's program No. 23 Electronics of nanosystems

Head of Laboratory - Doctor of Physical and Mathematical Sciences, Professor Shulakov Alexander Sergeevich .

Main directions of scientific research

• Experimental study of the fundamental laws of generation of ultrasoft X-ray radiation and its interaction with matter.
• Development of X-ray spectral methods for studying the atomic and electronic structure of short-range order in polyatomic systems (molecules, clusters), in solids on the surface, at hidden interphase boundaries and in the bulk.
• Development of the theory of X-ray processes.
• Processes studied and used: photoabsorption, photoionization and photoemission, external photoelectric effect, total external reflection, scattering, characteristic emission, inverted photoemission, generation of bremsstrahlung, threshold and resonant emission and photoemission.

For ease of perception, a story about how it was formed and by what the lab is busy into several parts:

Basic Concepts

Development of X-ray spectroscopy methods in St. Petersburg university

BASIC CONCEPTS

What is X-ray radiation (XR)?

X-ray radiation (XR), discovered by V.K. Roentgen in 1895 and still called foreign literature X-rays occupy the widest range of photon energies from tens of eV to hundreds of thousands of eV - between ultraviolet and gamma radiation. For achievements in the field of physics, the RI was awarded 8 (!) Nobel Prizes(the last prize was awarded in 1981). These studies largely shaped modern scientific and philosophical ideas about the world. X-ray radiation is not a product of natural radioactivity of a substance, but arises only in interaction processes. That is why RI is a universal means of studying the properties of matter.

There are two main mechanisms for the occurrence (generation) of RI. The first is the deceleration of charged particles in the Coulomb field of screened nuclei of atoms in the medium. Decelerating charged particles, in accordance with the laws of electrodynamics, emit electromagnetic waves perpendicular to particle acceleration. This radiation, called bremsstrahlung, has a high-energy boundary (the so-called short-wave boundary of bremsstrahlung), which coincides with the energy of the incident charged particles. If the particle energy is sufficiently high, then part of the very broad spectrum of bremsstrahlung is in the energy range of the CMB photons. Figure 1 schematically shows the process of formation of bremsstrahlung during electron scattering on an atom. The direction of emission and the energy of the photon are determined by a random variable - the impact parameter.

The second mechanism is the spontaneous (spontaneous) radiative decay of excited states of atoms of the medium that have a vacancy (hole) in one of the internal electron shells. One of such transitions is shown in Fig. 2 for an atom of type B. Typically, the Coulomb potential well of an atomic nucleus contains many levels, and the spectrum of the resulting X-ray radiation is therefore lined. Such RI is called characteristic.

RI absorption has photoionization character. Any electrons of a substance can take part in the absorption of X-ray radiation, but the most probable mechanism of absorption is photoionization of the inner shells of atoms.

Figure 2 shows a diagram of electronic transitions during the absorption of X-ray radiation by an atom of type A. It can be seen that the absorption edge is formed as a result of transitions of electrons of the inner shell to the lowest unfilled electronic state of the system (conduction bands in solids). The radiative transition shown in the figure involves electrons from the valence band, so the result is not a line, but a characteristic X-ray band.

X-ray spectroscopy

In 1914, the phenomenon of X-ray diffraction in crystals was discovered and a formula was obtained describing the diffraction conditions (formula Wolf-Bragg):

2dsin α = n λ , (1)

Where d is the interplanar distance of the reflecting atomic planes of the crystal, α is the grazing angle of incidence of the X-ray on the reflecting planes, λ is the wavelength of the diffracting X-ray, n is the order of diffraction reflection. Exactly crystals were the first dispersing elements for decomposing rays into a spectrum, widely used today.

The probability of transitions shown in Fig. 1, like any others, is expressed through integrals called matrix elements of the transition probability. These integrals have the following structure:

(Ψ i │ W │ Ψ f ) (2)

where Ψ i andΨ f - wave functions of the initial and final state of the system (before and after the transition), W - operator of interaction of an electromagnetic wave with an atom. As can be seen from Fig. 1, in the absorption process the final state contains a vacancy at the internal level, and in the emission process both states, initial and final, are excited (hole). This means that integral (2) is nonzero only in the region where the amplitudes of the states most localized near the nucleus with a vacancy on the inner shell are nonzero. This determines spatially local character of X-ray transitions and allows us to consider them as absorption or emission of specific atoms (see Fig. 2).

Typically, the symmetry of internal levels of atoms is classified within the hydrogen-like model by one-electron quantum numbers. Figure 2 shows sets of quantum numbers that characterize the symmetry of the levels of atoms A and B involved in transitions. The energy of these levels completely characterizes each atom; it is known and tabulated, as well as the energy of photons of characteristic lines, bands and absorption edges. That's why X-ray spectroscopy is the most effective method non-destructive analysis of the atomic chemical composition of objects.

In addition to the radial parts, the wave functions from (2) also contain angular parts, expressed by spherical functions. Matrix element (2) is not identically zero if certain relationships between quantum numbers characterizing the angular momenta of electrons are satisfied. For not too high photon energies (up to several KeV) transitions that satisfy dipole selection rules have the highest probability: l i - l f = ± 1, j i - j f = 0, ± 1. The lower the transition energy, the more strictly the dipole selection rules are satisfied.

From Fig. 2 it is clear that the spectral dependence of the absorption coefficient of X-ray radiation, as well as the spectral intensity distribution in the emission bands, should reflect the energy dependence distribution of the density of electronic states of the conduction band and density of states of the valence band, respectively. This information is fundamental to condensed matter physics. The fact that the processes of absorption and emission of X-ray radiation are local in nature and obey dipole selection rules, allow one to obtain information about local and partial (resolved by the angular momentum of electrons) densities of states of the conduction band and valence band. No other spectral method has such unique information content.

The spectral resolution in the X-ray region is determinedhardware resolution and, in addition, in the case of characteristic transitions (during absorption or emission), also natural width of internal levels, taking part in transitions.

Features of soft X-ray spectroscopy.

From formula (1) it is clear that the wavelength of radiation decomposed into a spectrum cannot exceed the value 2d. Thus, when using an analyzer crystal with a certain average value d = 0.3 nm, the region of photon energies less than approximately 2000 eV remains inaccessible to spectral analysis. This spectral range, called the soft X-ray region, has attracted the attention of researchers since the first steps of X-ray spectroscopy.

The natural desire to penetrate into the hard-to-reach spectral range was also enhanced by purely physical motives for its development. Firstly, It is in the soft X-ray region that the characteristic X-ray spectra of light elements from Li3 to P15 and hundreds of spectra of heavier elements, up to actinides, are located. Secondly, based on the uncertainty principle, we can conclude that atomic internal levels with low binding energy will have a smaller natural width than deeper levels (due to the shorter vacancy lifetime). Thus, movement into the soft X-ray region provides an increase in the physical resolution of X-ray spectroscopy. Thirdly, due to the existence of a simple relationship between energy, ∆ E, and wave, ∆ λ, intervals in the radiation spectrum:

∆ E= (hc/λ 2) ∆ λ, (3)

at a fixed wavelength instrumental resolution of the spectrometer∆ λ (determined by the width of the slots) increasing the wavelength of the analyzed X-ray radiation ensures a decrease in ∆ E, i.e. provides an increase in the hardware energy resolution of the spectra.

Thus, the region of soft X-ray radiation was represented as a spectroscopic paradise, in which conditions for maximum physical and instrumental resolution are simultaneously created.

However However, the acquisition of high-quality spectra in the soft X-ray region has been delayed for more than 40 years. These years were spent searching for high-quality dispersing elements and effective ways registration of radiation. Natural and artificial crystals with large d turned out to be too imperfect for high-quality decomposition of X-ray radiation, and the traditional photographic method of recording the intensity distribution dispersed RI - ineffective.

The result of the search was the use of diffraction gratings, and for its registration - detectors using the phenomenon of external X-ray photoeffect or photoionization processes in gases.

Ultrasoft RI, according to the proposal of A.P. Lukirsky, is called radiation with a photon energy from tens to hundreds of eV. As expected, penetration into the range of soft and ultrasoft X-ray radiation was indeed decisive for the formation of modern ideas about the electronic structure of polyatomic systems. The multielectron specificity of atomic processes involving shallow (subvalent) internal levels, clearly manifested in this spectral range, turned out to be unexpected. The many-electron theory is still based on experimental results obtained in the field of ultrasoft X-ray radiation. This process began with the work of A.P. Lukirsky and T.M. Zimkina, who discovered giant resonances photoionization absorption of X-ray radiation by multi-electron inner shells of inert gases.

The international community recognizes that the main contribution to the development of soft and ultrasoft X-ray spectroscopy methods was made by scientists St. Petersburg university and, above all, A.P. Lukirsky.

DEVELOPMENT OF METHODS OF X-RAY SPECTROSCOPY IN ST. PETERSBURG UNIVERSITY

P.I.Lukirsky And M.A.Rumsh

The future first head of the department, future academician Pyotr Ivanovich Lukirsky graduated from St. Petersburg University in 1916. First independent experimental study- the thesis, carried out by P.I. Lukirsky under the supervision of A.F. Ioffe, was devoted to the study of the electrical conductivity of natural and X-rayed rock salt. And further, work in the field of physics of X-ray radiation, physics of interaction of X-ray radiation with matter and X-ray spectroscopy attracted the attention of Pyotr Ivanovich throughout his entire creative life.

In 1925, the “Lukirsky capacitor” method, developed to study the energy distribution of photoelectrons, was used to detect soft X-ray radiation. For the first time, it was possible to measure the energy of the characteristic radiation of carbon, aluminum and zinc. The idea of ​​using photoelectron spectra of the internal levels of target-detector atoms to analyze the X-ray energy, implemented in these works, was fully realized and presented abroad as “fresh” only 50 years later.

Before 1929, works on X-ray dispersion and the Compton effect were published. In 1929, P.I. Lukirsky organized a department at the X-ray Institute (that was the name of the Physicotechnical Institute at that time!), in which studies of the diffraction of X-ray radiation, fast and slow electrons, as well as the study of the external X-ray photoeffect were carried out. These studies were also carried out at the University in the Department of Electricity, which he headed in 1934. They were instructed to lead to the young talented scientist Mikhail Aleksandrovich Rumsh.

After the war, M.A. Rumsh returned to the department in 1945. Through his efforts, an electron diffraction apparatus and an X-ray monochromator were assembled crystal analyzer. In 1952, a new student specialization was opened at the department - X-ray physics. Coursework and theses in this specialization were carried out on the basis of the X-ray laboratory created by M.A. Rumsh. It was this laboratory that became the prototype of the modern laboratory of ultrasoft x-ray spectroscopy. The bright, extraordinary personality of M.A. Rumsha, infectious efficiency and broad erudition, his brilliant lectures quickly made X-ray physics one of the most popular specializations at the faculty.

In 1962, Mikhail Aleksandrovich defended his doctoral dissertation on the topic “External X-ray photoeffect” based on a set of works. His works in this direction are recognized as classics throughout the world. They anticipated the advent of photoelectric effect spectroscopy and outlined the development paths for this area of ​​physics for many years to come. In the West, some of his research was repeated only 15-20 years later.

Photoelectric effect under conditions of dynamic scattering of X-ray radiation

At the end of the 50s, M.A. Rumsch proposed measuring the output of the external X-ray photoelectric effect under conditions of diffraction reflection of X-ray radiation from crystals. The angular dependences of the photoelectric effect output under conditions of diffraction of incident X-ray radiation are fundamentally different from those far from the Bragg angles and allow a more complete description of the diffraction scattering process. The highest sensitivity of the symbiosis of methods to violations of the crystalline order in the arrangement of sample atoms has made it a very effective tool for studying microelectronic materials.

For many years, work on the study of the X-ray photoelectric effect both in conditions of dynamic scattering and outside them was led by M.A. Rumsha’s student, associate professor Vladislav Nikolaevich Shchemelev. He created a theory of the photoelectric effect in the diffraction of X-ray radiation on crystals with disturbances and an almost complete semi-phenomenological theory of the usual external X-ray photoeffect in the photon energy range from hundreds of eV to hundreds of KeV. A talented but difficult person, Vladislav Nikolaevich never bothered to defend his doctoral dissertation, although in the world scientific community has long been considered a "living classic". V.N. Shchemelev died in 1997. Unfortunately, after his departure, work in the field of dynamic scattering of X-ray radiation in the laboratory died out. However, through the efforts of his students, they were developed in such scientific centers as the Physicotechnical Institute. A.F. Ioffe and the Institute of Crystallography of the Russian Academy of Sciences. A student of V.N. Shchemelev is the current director of this institute, Corresponding Member of the Russian Academy of Sciences M.V. Kovalchuk.

A.P.Lukirsky- founder of the scientific school of ultrasoft x-ray spectroscopy

In October 1954, after successful completion of graduate school, a young assistant, Andrei Petrovich Lukirsky, son of the first head of the department P.I. Lukirsky, began working at the department. The assistant began his scientific work in the X-ray laboratory of the department, headed by M.A. Rumsh. Subject scientific work was the development of techniques and methods for conducting spectral studies in the field of soft and ultra-soft X-ray radiation. This work, which continued the scientific interests of his father, despite the complexity and diversity of the problems facing him, was completed in just a few years. The key to success was the highest professional and human qualities of Andrei Petrovich, the atmosphere of creative search, dedication, clear and respectful relationships in the team created by him and M.A. Rumsh, and his ability to attract talented youth to the team.

The basis for the work was systems approach to solve emerging problems, optimize the operation of all nodes spectral devices based on the obtained experimental data on the properties of substances and materials. Consistent development of design solutions was carried out on the basis of operating experience of prototype units. To carry out the experiments, detectors and primitive universal measuring chambers with flat diffraction gratings were created. The Rowland scheme was chosen as the basic principle for constructing spectral instruments, which uses spherical gratings and mirrors to focus radiation and makes it possible to significantly increase the luminosity of the instruments.

At the preliminary stage, the following series of experiments were performed.

1. Spectral dependences of gas absorption coefficients for choosing the most effective filler for proportional gas-discharge counters of ultra-soft radioactive sources.
2. Spectral dependences of absorption coefficients of polymer materials for the optimal choice of material for counter windows.
3. Spectral dependences of the photoelectric effect output for selecting the most efficient photocathodes of secondary electron multipliers used for recording X-ray radiation.
4. Spectral dependences of the reflectances of polymeric materials and metals for choosing the most effective coatings of mirrors and diffraction gratings.
5. The operation of diffraction gratings in the ultrasoft X-ray region was studied in order to select the optimal groove shape.

It should be noted that although the motives for the research were of an applied nature, their results turned out to be undeniably valuable for fundamental science. Indeed, almost all measurements represented the first systematic studies in the field of ultrasoft X-ray radiation. They formed the basis of new scientific directions in X-ray spectroscopy, which are successfully developing to this day. And measurements of the absorption of soft X-ray radiation in inert gases became the subject of a discovery officially registered in 1984.

M.A. Rumsh, V.N. Shchemelev, E.P. Savinov, O.A. Ershov, I.A. Brytov, T.M. Zimkina, V.A. Fomichev, I took an active part in the research and testing. .I.Zhukova (Lyakhovskaya). All design work was carried out by Andrey Petrovich personally.

During Andrei Petrovich’s lifetime, two spectrometers were manufactured: RSL-400, on which the design of many components was worked out, and RSM-500. The spectrometer-m onochromator RSM-500 was intended to operate in the photon energy range from 25 to 3000 eV. Its design and optical characteristics turned out to be so successful that NPO Burevestnik produced the spectrometer in series for 20 years. Based on Andrei Petrovich's drawings, the RSL-1500 spectrometer was manufactured, which has unique characteristics in the spectral region from 8 to 400 eV. Figure 3 shows a diagram of this spectrometer, demonstrating the location of all the main components of any soft X-ray spectrometer.

The X-ray radiation, decomposed into a spectrum by a spherical diffraction grating, is focused on the Rowland circle. The position of the focus on this circle is determined by the wavelength of the X-ray radiation. At the input, the short-wave (high-energy) part of the X-ray radiation emitted by the sample (anode) is cut off by reflective filters and mirrors, which significantly increases the ratio of the useful signal to the background. The platform with the exit slit and replaceable detectors moves along the focusing circle.

The kinematic diagram of the RSM-500 spectrometer-monochromator, shown in Fig. 4, is solved in a completely different way.

Here the diffraction grating and the output slit block with detectors move in straight lines. This design allows for easy replacement of diffraction gratings to ensure maximum spectrometer performance over a wide spectral region. Lukirsky's spectrometers achieved a real energy resolution of less than 0.1 eV with excellent spectral quality. This result is a record to date.

Andrei Petrovich passed away in 1965 at the age of 37, full of new ideas and plans. Almost all studies carried out on Lukirsky spectrometers were pioneering in nature and are now assessed as classical. Most of them were completed after Andrei Petrovich's death by his students.

The invaluable contribution of A.P. Lukirsky to the development of spectral work using synchrotron radiation (SR) requires special mention. These works began to develop in the late 60s and now largely determine the face of modern science. In the early 70s, dozens of the world's leading spectroscopists visited the ultrasoft X-ray spectroscopy laboratory. The ideas and designs of Andrei Petrovich were accepted as the basis for the creation of soft X-ray SR monochromator spectrometers. These devices are now operating in hundreds of laboratories around the world.

Discovery by A.P. Lukirsky and T.M. Zimkina

When studying the absorption of soft X-ray radiation in Kr and Xe, an unusual form of absorption spectra was discovered near the 3d ionization threshold of Kr and the 4d threshold of Xe. The usual absorption jump at the threshold was absent, and instead a powerful broad absorption band appeared, located many eV above the ionization threshold of the indicated internal levels. The very first publication of the results in 1962 attracted the close attention of the widest scientific community. The discovered absorption bands, by analogy with nuclear physics, began to be called giant absorption resonances. Figure 5 schematically shows the appearance of the usual (expected) “single-electron” absorption spectrum and the shape of the giant resonance.

It turned out that the appearance of giant resonances cannot be explained within the framework of the one-electron theory of interaction of X-ray radiation with an atom. In Russia, Lithuania, the USA, Great Britain, and Sweden, groups of theorists were formed who, in intense competition, developed the theory of giant resonances. Their efforts, as well as new experimental results, showed that this phenomenon is universal in nature, determined by the specific type of effective potential of the electrons participating in the process. This is a two-valley potential with a barrier separating the inner deep potential well from the shallower outer one.
Figure 6 schematically shows the appearance of such a potential. A deep internal potential well contains bound excited (internal) states of atoms. The energy of some excited states turns out to be higher than the ionization potential in the region of continuous electronic states, but potential barrier holds them in the inner region of the atom for some time. These states are called autoionization states. Their decay occurs with the participation of the internal electrons of the atoms, which increases the total absorption cross section and leads to the appearance of a giant resonance.

In work led by T.M. Zimkina, giant absorption resonances were discovered in the spectra of rare earth atoms and actinides. These resonances are purely atomic in nature even in a solid. However, a two-valley type of potential can also be formed during the interaction of electrons of an absorbing atom with surrounding atoms. In this case, resonant phenomena of a polyatomic nature arise.

At the end of the 70s, German physicists, using the SR storage ring DESY in Hamburg, experimentally proved the multielectron nature of the giant absorption resonance phenomenon. Since then, resonance phenomena in photoemission have been actively studied to this day.

The giant absorption resonances discovered in 1962 and their further detailed experimental study served as the impetus for the formation of modern multi-electron concepts of atomic processes. They determined the direction of development of physics for 40 years ahead.

In 1984, the results of studies of giant absorption resonances were registered by the USSR Civil Code for Inventions and Discoveries as a discovery.

Official recognition of the achievements of A.P. Lukirsky’s school

The works of A.P. Lukirsky and his students are well known to the international scientific community, their priority and outstanding contribution to the development of physics are generally recognized. This informal reputation of the school is undoubtedly its most valuable achievement. However, already the first scientific results obtained thanks to methodological developments A.P. Lukirsky, were highly appreciated by colleagues and the scientific community at the official level.

In 1963, the All-Union Conference on X-ray Spectroscopy adopted a special decision in which the work of A.P. Lukirsky’s group was presented as “a powerful breakthrough in the most important area of ​​research,” and the field of ultrasoft X-ray spectroscopy was designated as the most promising area of ​​research in the future.

In 1964, a similar resolution, at the insistence of one of the most prominent theorists in the world, Hugo Fano, was adopted by the International Conference on Collisions of Atoms and Particles.

In 1964, A.P. Lukirsky The first prize of Leningrad State University was awarded for scientific research.

In 1967, M.A. Rumsh and L.A. Smirnov were awarded the USSR Council of Ministers Prize for research work that ensured the creation of the first Soviet quantum meters.

In 1976, the Lenin Komsomol Prize for the development of work in the field of ultrasoft x-ray spectroscopy was awarded to V.A. Fomichev.

In 1984, the USSR Civil Code for Inventions and Discoveries registered under number 297 the discovery of A.P. Lukirsky and T.M. Zimkina “The pattern of interaction of ultrasoft X-ray radiation with multi-electron shells of atoms” of 1962 priority.

In 1989, T.M. Zimkina and V.A. Fomichev were awarded the State Prize of the Russian Federation for the development of X-ray spectral methods for studying chemical bonds.

A successful public defense of a dissertation is not only recognition of the applicant’s high qualifications, but also evidence of the high scientific level of the scientific school that educated the applicant. Over the years of the laboratory's existence, 50 candidate's and 13 doctoral dissertations were defended.

TODAY AND TOMORROW LABORATORIES

Today there are 5 doctors working in the laboratory physics and mathematics sciences,professors, and 4 candidates of physical and mathematical sciences.

The laboratory is headed by Prof. A.S.Shulakov.

The areas of work and processes under study are listed at the very beginning of the review.In conclusion, let us dwell on the current promising strategic and tactical tasks.

The prospects for the development of any scientific direction are determined by the volume and quality of scientific results obtained yesterday and today, the ability of the authors to have a broad vision of the place of the results of their efforts in modern science, their demand, an adequate assessment of the corridor of opportunities and, of course, ambitions. Things are going well with these conditions in LUMRS so far, so we will detail the immediate development prospects.

Two main interpenetrating areas of activity of the laboratory can be distinguished: the development of new methods for studying complex multiphase solid-state systems and the application of X-ray spectral methods to the study of the electronic and atomic structure of topical nanostructured materials. The first direction should include, first of all, the development of theoretical concepts and models for describing the processes underlying spectral methods.

High-resolution X-ray spectroscopy is a unique tool for studying changes in the electronic and atomic structure of free molecules when they are introduced into nano and macro-sized systems Therefore, further studies of the interaction of X-ray radiation with matter will primarily be associated with the study of such complex systems. The quasi-atomic model seems promising for studying correlations between the electronic subsystem and the finite motion of the embedded molecule, its vibrations and rotations inside the capsule. Particular attention will also be paid to the processes of interaction of radiation from X-ray free electron lasers and their use for studying the electronic and atomic structure of molecules and clusters and the dynamics of their X-ray excitations.

In recent years, within the framework of the theory of X-ray radiation, new ideas have emerged for describing the processes of formation of X-ray emission bands and absorption spectra of compounds and complex materials. It is necessary to develop these ideas, including into the theoretical sphere calculations of Auger channels for the decay of core states and other multielectron dynamic processes. The end result of these efforts may be the creation of new methods direct definition values ​​of partial effective atomic charges in compounds and a significant increase in the accuracy and reliability of interpretation of experimental data.

In an experiment in last years a sought-after direction for the development of non-destructive layer-by-layer analysis methods has crystallized surface layers nanometer thickness (nanolayers). The methods of X-ray emission spectroscopy and X-ray reflectance spectroscopy (XRAS), which allow layer-by-layer phase analysis, have proven to be very effective. chemical analysis, which is very rare. First, trial calculations demonstrated the information content of the SORI calculated from the spectral-angular dependences atomic profiles. And at the same time, a number of problems were revealed, the main one of which is the impossibility at this stage of research to separate the effects of small-scale roughness and the fine structure of the interface in the reflection coefficient. There is an obvious need for further development of experimental and theoretical approaches to the method to fully understand the role of surface roughness and interdiffusion of materials in the formation of interphase boundaries in nanosystems. The main objects of application of depth-resolved X-ray spectral methods in the coming years will be nano-cohesive systems of various purposes and varying complexity.

The elemental base for the synthesis of many promising nanoobjects is formed by polyatomic systems based on compounds of light atoms of boron, carbon, nitrogen, oxygen, etc., as well as 3 d-transition atoms, the absorption spectra of which are located in the ultrasoft X-ray region of the spectrum (nanoclusters, nanotubes and nanocomposites based on them, low-dimensional systems on the surface of single crystals of semiconductors and metals, composites based on layered (graphite, h-BN, etc.) and fullerene-containing materials, molecular nanomagnets based on complexes of transition and rare earth metals, nanostructures based on organometallic complexes of porphyrins, phthalocyanines, salens, etc., ordered arrays of catalytically active nanoclusters, nanostructures for molecular electronics and many others). In this area, the capabilities of X-ray absorption spectroscopy (atomic selectivity, the ability to isolate electronic states with a certain angular momentum relative to the absorbing atom, sensitivity to the atomic structure of its immediate environment and magnetic moment absorbing atom) are most fully manifested. Thanks to this, X-ray absorption spectroscopy using SR will remain popular in a number of cases as an indispensable method for the experimental study and diagnostics of the atomic, electronic and magnetic structure of nano-sized systems and nanostructured materials.

LURMS team today

Belong to school Rumsha-Lukirsky-Zimkina great honor and luck. Currently, the laboratory is staffed mainly by Tatyana Mikhailovna’s students and students of her students.

The first of them, of course, is Doctor of Physics and Mathematics. Sciences, Professor Vadim Alekseevich Fomichev. He was lucky enough to begin student research under the guidance of A.P. Lukirsky. Vadim defended his diploma in December 1964. A bright, talented and enthusiastic person, in 1967 he defended his PhD thesis on the topic “Study of the energy structure of binary compounds of light elements using ultrasoft X-ray spectroscopy.” And in 1975 - his doctoral dissertation “Ultrasoft X-ray spectroscopy and its application to the study of the energy structure of solids. Under his leadership, the RSL-1500 spectrometer, the latest development of A.P. Lukirsky, was launched, and all methods of ultrasoft X-ray spectroscopy were mastered and advanced. In 1976, Vadim Alekseevich was awarded the title of laureate of the Lenin Komsomol Prize in the field of science and technology. Just like Tatyana Mikhailovna, in 1988 he became a laureate of the Russian State Prize for

development of technology and methods of X-ray spectral research, awarded the Order of the Badge of Honor and medals.

Vadim Alekseevich devoted many years to administrative work. First, as deputy dean of the physics department, and then, in the most difficult years, from 1978 to 1994 he worked as director of the Research Institute of Physics. V.A. Foka (The Institute was then an independent legal entity). Now he holds the post of Deputy Vice-Rector of St. Petersburg State University, but does not break ties with the laboratory. In the photograph, Vadim Alekseevich is caught at a department seminar.

The elder of the scientific and pedagogical workshop of LURMS is the tireless and cheerful candidate of physical and mathematical sciences, associate professor and senior Researcher Evgeny Pavlovich Savinov. He was lucky enough to make a significant contribution to the development of A.P. Lukirsky’s project. Together with M.A. Rumsh, V.N. Shchemelev, O.A. Ershov and others, he took part in measurements of the quantum yield of various materials to select effective soft X-ray detectors, as well as in experiments to study the reflectivity of coatings for optical elements spectrometers.

The study of the phenomenon of the external X-ray photoelectric effect became the main field of activity of Evgeniy Pavlovich for many years. His PhD thesis (1969) was devoted to the study of the statistics of the X-ray photoelectric effect.

Breaks in scientific and pedagogical activity at the University arose only as a result of the need to sow the rational, the good, the eternal on the African continent. This, however, did not stop him from raising two physicist sons. In recent years, Evgeniy Pavlovich has successfully engaged in new work in the field of ultrasoft X-ray spectroscopy.

Another student of Tatyana Mikhailovna, Fomichev’s classmate, candidate of physical and mathematical sciences, associate professor Irina Ivanovna Lyakhovskaya, also began working as a student under Andrei Petrovich. Her area of ​​scientific interest was the electronic structure of complex

transition metal compounds. She has been involved in many pioneering studies in the fields of X-ray absorption spectroscopy, ultra-soft X-ray emission spectroscopy, soft X-ray emission and reflectance spectroscopy. She was distinguished by extreme thoroughness and thoughtfulness of her research.

In recent years, Irina Ivanovna has devoted all her best qualities to organizational and methodological work at the physics faculty and department, bringing great and highly valued benefits. Over the years of dedicated work for the benefit of the department, she became younger, earned the respect of her colleagues and the love of students.

Alexander Stepanovich Vinogradov, Doctor of Physics and Mathematics. sciences, professor, became

leader of the generation that had not seen A.P. Lukirsky. He began his scientific work under the guidance of T.M. Zimkina. The main area of ​​his scientific interests is the study of the patterns of formation of X-ray absorption spectra and their use to study the features of the electronic and atomic structure of polyatomic objects. The results of reflection and research were summarized in his doctoral dissertation “Shape resonances in the near-field fine structure of ultrasoft X-ray absorption spectra of molecules and solids” (1988).

In recent years, the objects of research by A.S. Vinogradov have become various nanostructured materials and coordination compounds of atoms of transition elements (cyanides, porphyrins, phthalocyanines, salenes), and the palette of research technologies was replenished with methods of electronic (photoelectronic and Auger) spectroscopy and fluorescence. In research practice he uses only the equipment of synchrotron radiation centers.

Doctor of Physics .- Mathematical Sciences, Professor Alexander Sergeevich Shulakov appeared at LURMS 3 years later than A.S. Vinogradov. His first mentor was V.A. Fomichev, and

the topic that determined further passions was ultrasoft X-ray emission spectroscopy of solids. X-ray spectroscopy excited by electron beams is perhaps the most complex and capricious method in the family of X-ray spectroscopy methods. Therefore, achieving success in this field is especially honorable.

After defending his PhD thesis, Alexander Sergeevich changed his traditional field of research to search for new methods for obtaining information about the electronic structure of solids. His doctoral dissertation “Ultrasoft X-ray emission spectroscopy with varying excitation energy” (1989) summarized the first results of this search. The direction turned out to be fruitful, and it is still developing today. Of the achievements, the author's greatest satisfaction is the discovery of the phenomena of atomic polarization bremsstrahlung and resonant inverted photoemission, as well as the world's first registration of X-ray emission bands on the surface of single crystals of rare earth metals.

In 1992, A.S. Shulakov was elected head of the ETT department and appointed head of LUMRS.

The next generation of the LURMS team carried out their first and candidate research with the participation and guidance of T.M. Zimkina. But they spent most of their creative life and carrying out their doctoral research without Tatyana Mikhailovna. This is A.A. Pavlychev and E.O. Filatova.

Doctor of Physics .- Mathematical Sciences, Professor Andrei Alekseevich Pavlychev is the only “pure” theoretician of the department. His first mentors were T.M. Zimkina and A.S. Vinogradov. From a young age, Andrey showed a penchant for dust-free theoretical work, and he was given the opportunity to master methods of theoretical analysis of spectra photoionization absorption of X-ray molecules.

Andrey took full advantage of this opportunity.

Following the traditional path, he quickly noticed that generally accepted concepts poorly reflect the main specificity of photoionization of the inner shell of an atom, which consists in the formation of spatially highly localized excitations that are highly sensitive to short-range order in a solid.

The quasi-atomic model developed by A.A. Pavlychev is based on the atomic photoelectric effect, the spectral and angular dependence of which is distorted by the influence of the external field created by all neighboring atoms. The main provisions of the model were outlined by the author in his doctoral dissertation “Quasian-atomic theory of X-ray absorption spectra and ionization of the internal electron shells of polyatomic systems,” successfully defended in 1994. This flexible model often allows one to solve complex problems in an analytical form that are hardly amenable to traditional theoretical methods. Now the model has received wide international recognition, but work to improve it continues and remains in demand and fruitful.

The main scientific specialization of Doctor of Physical and Mathematical Sciences, Professor Elena Olegovna Filatova since her student years has been reflectometry in the field of soft X-ray radiation. With the help of her first mentors, T.M. Zimkina and A.S. Vinogradov, she managed to restore this scientific direction, which was successfully developing during the time of A.P. Lukirsky.

Elena spent a lot of effort to get absolute values optical constants. (As you know, measuring the absolute values ​​of something in physics is equivalent to a feat). However, this work suggested to Elena Olegovna that the capabilities of reflectometry are far from being limited to this kind of measurements. It became obvious that it can be turned into X-ray reflection and scattering spectroscopy, which makes it possible to obtain a variety of information about the electronic and atomic structure of real and nanostructured materials. The development of this new direction of soft X-ray spectroscopy was devoted to the doctoral work of E. O. Filatova “Spectroscopy of specular reflection and scattering of soft X-ray radiation by surfaces of solid bodies” (2000).

The work of Elena Olegovna’s group harmoniously combines the capabilities of the RSM-500 laboratory spectrometer, modified to carry out spectral-angular dependences of reflection, scattering and photoelectric effect output, and the use of equipment from synchrotron radiation centers abroad.

Recognition high level Elena Olegovna's work was her invitation to the Scientific Commission of the most representative joint International Conference on the physics of ultraviolet radiation - X-ray and intra-atomic processes in matter ( VUV-X).

The younger generation of employees did not know T.M. Zimkina. This is A.G. Lyalin and A.A. Sokolov.

Andrey Gennadievich Lyalin, candidate of physical and mathematical sciences, senior researcher at LUMRS, with difficulty and perseverance completed an excellent experimental thesis

work under the leadership of A.S. Shulakov. It was devoted to the study of a strange line spectrum of radiation that appears in the region of 8 – 15 eV when a number of rare earth metals and alkali hydroxides are irradiated with electrons.

However, the flawless execution of a unique experimental study showed that in terms of his internal potentials, Andrey gravitates more towards theoretical work. Therefore, already in graduate school, he was asked to create a theory of atomic polarization bremsstrahlung. With the help of theorists from the group of M.Ya. Amusya, Andrei quickly got used to new area and began to produce interesting results, summarized in his Ph.D. thesis “The Theory of Atomic Polarization Bremsstrahlung of Rare-Earth Metals” (1995).

This work initiated his interest in the general theory of giant resonances in multivolume systems. Very talented and efficient, Andrei Gennadievich, a Presidential Scholar during his student and graduate years, began to easily win international grants and managed to work in the best theoretical groups in Germany, England, and the USA. He is still responsible at LUMRS for the development of the theory of the electronic structure of clusters and their interaction with particles and radiation.

Andrey Aleksandrovich Sokolov, candidate of physical and mathematical sciences, assistant at the ETT department, works in the group of E.O. Filatova. Just like Andrei Lyalin, he was a Presidential Scholar, but his element is experimentation.

Andrey is a very lively, active and organized person. It successfully copes with both laboratory equipment that requires particularly careful maintenance and modernization, and with various installations of synchrotron radiation centers. In 2010 he defended his thesis “Study of the electronic and atomic structure of the interphase boundaries of nanolayers synthesized on silicon.” Has a very high potential in setting up and conducting complex experimental studies.

Figure 7 shows what information can be obtained about molecular gases, adsorbents, the surface of solids, coatings, hidden interphase boundaries, the properties of solids in the bulk and the properties of various types of interstitials using ultrasoft X-ray spectroscopy methods. This figure clearly demonstrates the versatility and unique information content of these methods, and the great prospects for their further development.

Currently, the laboratory has three spectrometers RSM-500, spectrometers RSL-400 and RSL-1500, a measuring chamber with a flat diffraction grating, a crystal monochromator for studying the photoelectric effect under dynamic scattering conditions and other unique equipment.

Over the past 5 years, the laboratory has received 8 RFBR grants.Over the past 3 years, 4 articles by laboratory staff have been published in the most prestigious physics journal Physical Review Letter.

For the future of the laboratory, it is undoubtedly important to have a deep history and traditions, the presence of an established and recognized scientific school, and the presence of original ideas and plans among the current leaders of the work. However, the realization of the future is in the hands of the younger generation - employees, graduate students, and students.