Kochur, A G

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Okost M., Shapovalov V., Morozov A., Vasilchenko A., Kochur A., Yavna V.

This work is devoted to the determination and systematization of the properties of clay soils used in the construction of new railway tracks in order to develop the railway network in the Azov-Black Sea region of Russia. To this end, classification characteristics have been determined by traditional laboratory methods and the possibility of soil swelling under excessive moisture has been estimated. In addition, the compressibility of soils has been studied as the main factor ensuring the trouble-free operation of the subgrade of railways during their long-term operation. Soil samples for measurements were taken from open pits located near construction sites at an extended length of construction of 530 km. The new regression relations proposed in the work provide in some cases the accuracy of determining the soil characteristics close to the accuracy of laboratory tests. They may be in demand when monitoring the accuracy of laboratory tests of soil properties of other open pits and to increase the speed of pre-design surveys during further development of the railroad network in this region.

Googlev K., Kozakov A., Kochur A.G., Nikolskii A.V., Rudskaya A., Shevtsova S.I.

Abstract Complex manganites A1−xCdxMnO3 (A = Pr, La) are synthesized by solid state reaction method. X-ray diffraction, scanning electron microscopy and energy-dispersive analysis are applied to study their crystal structure, surface morphology, elemental and phase composition. X-ray photoelectron spectroscopy (XPS) methods are used to study the charge states of Pr and La cations, as well as to quantify the fractions of coexisting Mn3+ and Mn4+ ions. La3d-, La4d-, Pr4d- и Mn2p-spectra of La3+, Pr3+, Mn3+ and Mn4+ ions are calculated in the isolated–ion approximation with accounting for multiplet splitting and charge transfer effect. Good agreement with the experiment is obtained. The relative fractions of trivalent and tetravalent manganese ions in La0.45Cd0.78Mn0,9O2.86 and Pr0.50Cd0.76Mn0.86O2.88 samples are determined by fitting the Mn2p spectra by superposition of experimental spectra containing only Mn3+, and only Mn4+ ions; they were found to be 0.71Mn3+/0.29Mn4+ and 0.54Mn3+/0.46Mn4+, respectively.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

The formation of multiply charged Agq+ ions resulting from photoionization and subsequent cascade decay of inner-shell vacancy states is studied using the method of construction and analysis of the cascade decay trees. Cross sections for the cascade production of Agq+ ions, yields of Agq+ ions, and mean photoion charge are calculated as functions of incident photon energy in the range of 70 eV to 100 keV. The results of this study are relevant for developing the strategies of radiotherapy using Ag-based radiosensitizers.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Abstract Ion yields upon the cascade decays of single vacancies in K to O shells of an isolated iodine atom are calculated by the method of construction and analysis of the cascade decay trees. Branching ratios needed for the simulations are calculated based on Pauli–Fock partial transition widths. Partial photoionization cross sections are calculated with accounting for the core relaxation effect and used to calculate the cross sections of I q+ photoions production in the 0.01–100 keV incident photon energy range. Accounting for the spin-orbit splitting and the splitting due to electron-electron interaction is shown to be important when calculating mean energies and probabilities of the transitions between energetically closely lying ionic configurations. On the other hand, inclusion of the additional shake-off electron ejections, in spite of complicating severely the decay trees, is found to affect little calculated cascade ions production probabilities.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

We have performed the Monte Carlo simulation of the processes of secondary ionization of water induced by cascade decays of inner-shell vacancies in an iron atom placed in water. We have obtained the spectra of electrons and photons emitted during the decay of vacancies in the K and L shells of the iron atom. The dependences of the number of secondary ionization events and the energy absorbed as a result of these processes on the radius of the sphere in which such processes occur have been calculated. The decay of a single 1s vacancy in an iron atom generates on the average 232 events of secondary ionization induced by an electron impact, in which the energy of 3274 eV is absorbed, as well as 18 secondary photoionization events, in which the energy of 256 eV is absorbed. The dependences of the dose absorbed in water on the distance from the iron atom have been calculated.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

Cascade decays of single vacancies in the K, L, M, and N shells of the silver atom are studied using the method of straightforward construction and analysis of the cascade de-excitation trees with inclusion of additional shake-off ejections of outer-shell electrons caused by the change of atomic core potential due to cascade transitions. The spectra of the cascade-produced electrons and photons emitted upon the decay of single vacancies in 1s1/2 to 4p3/2 subshells are calculated. For each initial vacancy, the energies absorbed by the silver atom itself, and those carried away by cascade electrons and photons, are calculated. Absorption of energy by the silver atom itself is only significant upon N- and M-shell ionization (49–66% and 18–36%, respectively), i.e. in the UV to soft X-ray range. After L- to N-ionization, most of the acquired energy is reemitted with cascade electrons, respective portions making 81–85% during L-ionization, 62–82% during M-ionization, and 34–51% during N-ionization. Reemission of energy with cascade photons is dominant after K-ionization (76%). When silver atoms are used as radiosensitizing agents in radiotherapy, cascade electrons play the principal role in the energy transfer to organism tissues. Due to small free paths in the organic medium, they give their energy to the environment in rather small volumes inside a particular cell where they are placed. As for the photons emitted after K-ionization, they transfer energy to the medium in much larger volumes, and with much smaller absorbed doses.

Morozov A.V., Olkhovatov D.V., Shapovalov V.L., Kochur A.G., Yavna V.A.

Morozov A., Shapovalov V., Popov Y., Kochur A., Yavna V.

The aim of the study is to determine the correlations between mechanical impacts on clay soil samples and resulting changes in the microstructure of the samples and their IR spectra. For research, soil from a railway subgrade under construction in the Azov-Black Sea region was used. The soil was examined by traditional and modern physical methods and classified as light clay. Clay properties were modified by adding alabaster to the soil, after which the samples with different amounts of alabaster were subjected to mechanical load. A cyclic mechanical impact by the compression method was applied to a clay sample without alabaster, an equivalent to the passage of 400 freight trains along the railway track. The microstructure of samples was studied by electron microscopy which allowed determining the microstructure parameters of the fragments of samples before and after the mechanical action. Samples of clay and clay with the addition of alabaster were subjected to a semi-quantitative express analysis by IR spectroscopy, as a result of which the concentrations of minerals were determined with an accuracy of no worse than 10%. Clay and clay samples with the addition of alabaster were subjected to static uniaxial compression, after which the samples were examined by IR spectroscopy. Comparison of the results of spectral and compression studies made it possible to investigate the correlations between changes in the peak intensities of the IR spectra bands and the concentration of alabaster, as well as the strength properties of the soil.

Yavna V., Shapovalov V., Okost M., Morozov A., Ermolov Y., Kochur A.

Subgrade is an important construction element of the railroad track. In the process of long-term operation, the subgrade is loaded by trains and exposed to natural climatic factors, such as wind and seismic loads, moisture caused by atmospheric precipitations and groundwater, exposure to positive and negative temperatures. At the same time, the subgrade must provide reliability and stable properties of the railway track because its renovations are the most expensive ones among those for the railway track in general. Due to this fact, national regulatory documents for the construction of the subgrade impose strict requirements on its deformity for the entire duration of modern railways operation. One of the ways to solve this problem on the stage of construction designing is computer predictive modelling of structural behavior that considers the changes of its elements and properties of construction materials under the long-term train impact taking into consideration the varying natural climatic factors. In this review, we analyze accumulated scientific and technical experience in formulating optimal approaches to the determination of initial data for computer simulation of repeated impact of the train loads for predicting railway track subgrade deformation considering engineering-geological conditions and natural climatic factors. We describe the stages of creating the subgrade computer modelling taking into account the analysis of trains load impact, the properties of model’s structural layers, and the change of soil properties under long-term loads.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

Abstract Cascade decays of single vacancies in K to O shells of the gold atom are simulated by straightforward construction and analysis of the cascade decay trees. Portions of energies a) absorbed by initially ionized Au atom, b) reemitted by cascade-produced electrons, and c) reemitted by cascade-produced photons are calculated with taking into account the shake-off processes caused by the change of atomic core potential during cascade transitions. Au atom absorbs noticeable amount of energy acquired in photoionization act only when ionized in its N and O shells, 33–45% and 41–54%, respectively. Except for the case of K-ionization, most of the energy is reemitted by cascade electrons: 57–64%, 77–85%, 55–67%, and 46–59% during the decay of vacancies in L, M, N, and O shells. Energies carried away by the cascade photons are only important for initial vacancies in K (89%) and L (29–39%) shells. Inclusion of the shake-off branches in the decay trees increase substantially their complexity, however it leads to comparatively small corrections to calculated portions of energy redistributed through channels a, b, and c. This supports earlier qualitative prediction of small possible effect of the SO processes on the cascades in heavy atoms.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

Abstract Final ion yields and mean final ion charges upon the cascade decay of single vacancies in the K, L, M, and N shells of atomic silver are calculated using the method of construction and analysis of the decay trees with accounting for the shake-offs caused by the change of atomic core potential due to cascade transitions. The shake-off effect on the final ion yields is found to be comparatively small, the largest increase of the mean final ion charge being 0.20e in the case of initial 2s vacancy. Total semi-relativistic Pauli–Fock energies of cascade-produced ionic configurations were used to calculate cascade transition energies, which made it possible to accurately account for the closing of some non-radiative transitions in multivacancy cascade configurations. For the transitions with overlapping multiplets of initial and final ionic configurations, only energetically allowed transitions between the multiplet components were counted when calculating mean transition energies and transitions branching ratios. Comparison of calculated charge spectra with those reported earlier by other authors demonstrated crucial importance of accurate calculation of transition energies and accounting for multiplet splitting in simulation of cascades in heavy atoms.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

A method of straightforward construction and analysis of the cascade decay trees is applied to calculate photon and electron spectra emitted upon the cascade de-excitation of single inner-shell vacancies in the gold atom produced by photoionization. The energy acquired by the gold atom upon photoionization is split into the following channels: i) energy absorbed by the gold atom itself, ii) energy carried away by the cascade electrons, and iii) energy carried away by the cascade photons. The energies absorbed through channels i–iii are analyzed for the cascade decay of each single vacancy in O to K shells, and presented as functions of incident photon energies based on calculated partial photoionization cross sections. Energy reemitted through channels ii and iii in the cases of O-, N-, M-, L-, and K-ionization make, respectively, 47–60%, 55–69%, 85–89%, 94–96%, and 99% of the initially acquired energy. Cascade-produced electrons and photons eventually transfer their energy to the medium which lays the base for using gold-containing compounds and gold nanoparticles as radiosensitizing agents in radiotherapy. Cascade-produced electrons, as well as photoelectrons, are found to be the principal transmitters of energy to atoms of the environment in the vicinity of the sites of initial ionization. Their relative role in possible radiosensitizing effect is analyzed on the incident photon energy range of 0.01–1000 keV.

Tutumluer E., Wang H., Husain S.F., Kong T., Kim Y., Ding K., Qamhia I.I., Wilk S., Li D.

Bashal A.H., Khalafalla M.A., Ibrahim R.M.

Pradhan P.K., Panda A.B., Mishra G.K., Mohanty N.K.

Ode A.B., Hamers R.J.

Wunsch K., Roguska A., Chodun R., Skołek E., Marciniak S., Kulikowski K., Sobiecki J.R.

Gyulasaryan H., Tolchina D.B., Avakyan L.A., Srabionyan V.V., Bugaev L.A., Kozakov A.T., Nikolskiy A.V., Mikheykin A.S., Pankov I.V., Tsaturyan A.A., Emelyanov A.V., Chumakov R.G., Mukasyan A.S., Manukyan A.S.

Liu Y., Liang X., Du Y., Wang Y., Chen Z., Wang Z., Wang H., Gu X., Sun J., Zhang J., Liu X.

Wu Q., Li C., Guo W., Ma Y., Zhao L., Pan N., Cheng N.

Nie K., Zhang X., Zhang X., Zhang X., Wang L., Xu J., Mei L., Wang H.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Kasprzhitskii A., Lazorenko G.

Bashal A.H., Khalafalla M., Habeeb T., Ibraheem A.M.

Panagopoulos V., Sigalos A., Anyfantis D.I., Niarchos D.

Fe2P (iron phosphide) alloys have garnered significant interest in recent years due to their potential applications in permanent magnet materials, particularly in the context of energy-efficient and environmentally friendly technologies. We have sought to tailor the magnetic properties, such as magnetization, coercivity, and Curie temperature, to meet the specific requirements of rare-earth-free permanent magnets for various industrial sectors. In this work, we review recent advancements in the exploration of substitutions (Si, Co, Mn, and Ni) within Fe2P alloys aimed at enhancing their magnetic performance as candidates for permanent magnets. The X-ray patterns of (Fe,Co)2P show great crystallinity with a pure Fe2P phase even with Mn and Ni substitutions. The Fe2P structure crystallizes in the P-62m space group. It has been confirmed that the transition metals substitute the 3g Fe-site, sometimes with adverse effects regarding magnetic properties with Co vs. Ni substitution, and that Si substitutes the 2c P-site. The saturation magnetization increases (MS=87 Am2/kg) with Mn substitution, while the Curie temperature decreases with these substitutions. The impact of various substitutional elements on the magnetic properties of Fe2P alloys is highlighted, and challenges encountered in this field are reported.

Indraratna B., Xu B., Rujikiatkamjorn C.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Okost M., Shapovalov V., Morozov A., Vasilchenko A., Kochur A., Yavna V.

This work is devoted to the determination and systematization of the properties of clay soils used in the construction of new railway tracks in order to develop the railway network in the Azov-Black Sea region of Russia. To this end, classification characteristics have been determined by traditional laboratory methods and the possibility of soil swelling under excessive moisture has been estimated. In addition, the compressibility of soils has been studied as the main factor ensuring the trouble-free operation of the subgrade of railways during their long-term operation. Soil samples for measurements were taken from open pits located near construction sites at an extended length of construction of 530 km. The new regression relations proposed in the work provide in some cases the accuracy of determining the soil characteristics close to the accuracy of laboratory tests. They may be in demand when monitoring the accuracy of laboratory tests of soil properties of other open pits and to increase the speed of pre-design surveys during further development of the railroad network in this region.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

Abstract Ion yields upon the cascade decays of single vacancies in K to O shells of an isolated iodine atom are calculated by the method of construction and analysis of the cascade decay trees. Branching ratios needed for the simulations are calculated based on Pauli–Fock partial transition widths. Partial photoionization cross sections are calculated with accounting for the core relaxation effect and used to calculate the cross sections of I q+ photoions production in the 0.01–100 keV incident photon energy range. Accounting for the spin-orbit splitting and the splitting due to electron-electron interaction is shown to be important when calculating mean energies and probabilities of the transitions between energetically closely lying ionic configurations. On the other hand, inclusion of the additional shake-off electron ejections, in spite of complicating severely the decay trees, is found to affect little calculated cascade ions production probabilities.

Suresh S., Vindhya P.S., Kavitha V.T.

Present study reports the combustion synthesis of lanthanum manganite (LaMnO3) perovskites with rhombohedral structure having R-3 C space group. The structural and morphological evaluations of synthesized nanoparticles were done by XRD, FTIR, SEM and XPS. The BDS analysis reveals different types of polarization associated with dielectric properties. Frequency-dependent dielectric properties such as dielectric constant, dielectric loss, ac conductivity and capacitance were analyzed at room temperature. BDS analysis explain Maxwell-Wagner effect and Jhonscher universal power law. Room temperature and low temperature magnetic properties were investigated using VSM. M(T) measurements shows second order phase transition from ferromagnetic (FM) to paramagnetic (PM) at 230 K Curie temperature. The detailed magnetic characteristics of lanthanum manganite perovskites were clearly explained by Curie – Wiess and Arrott's plot. The hyperthermial behavior were studied with normal and pre-heated LaMnO3. The in - vitro anticancerous analysis were explained by MTT assay. The LC50 values of normal and preheated specimens are 124.145 µg/ml and 86.159 µg/ml, respectively. The reduction in LC50 value of preheated sample underscores its superior anticancer efficacy compared to normal sample.

Masrour R., Kadim G., Ellouze M.

The magnetic, electronic, structural, thermoelectric properties and magnetocaloric effect of Pr0.75Ba0.25MnO3 perovskite using, experimental, DFT calculation and Monte Carlo simulations were investigated. The ground state has half-metallic character. Our calculations also show that the Pr0.75Ba0.25MnO3 has a ferromagnetic behavior. Pr0.75Ba0.25MnO3 exhibits p-type behavior with dominant holes as the primary carriers, as indicated by its thermoelectric properties. This system exhibits a ferromagnetic–Paramagnetic transition. We have successfully obtained several properties, including magnetization, specific heat, variation of specific heat, magnetic entropy changes, relative cooling power, and the magnetic hysteresis cycle. For a magnetic field change of 5 T, the maximum value of the magnetic entropy change (∣ΔSmax∣) was approximately 12 J/kg.K, while the relative cooling power (RCP) reached 126 J/kg. The promising potential of the present system for magnetic refrigeration is evident due to its relatively large values of ∣ΔSmax∣ and RCP. Finally, the thermoelectric properties were given.

Chaynikov A.P., Kochur A.G., Dudenko A.I.

We have performed the Monte Carlo simulation of the processes of secondary ionization of water induced by cascade decays of inner-shell vacancies in an iron atom placed in water. We have obtained the spectra of electrons and photons emitted during the decay of vacancies in the K and L shells of the iron atom. The dependences of the number of secondary ionization events and the energy absorbed as a result of these processes on the radius of the sphere in which such processes occur have been calculated. The decay of a single 1s vacancy in an iron atom generates on the average 232 events of secondary ionization induced by an electron impact, in which the energy of 3274 eV is absorbed, as well as 18 secondary photoionization events, in which the energy of 256 eV is absorbed. The dependences of the dose absorbed in water on the distance from the iron atom have been calculated.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

Cascade decays of single vacancies in the K, L, M, and N shells of the silver atom are studied using the method of straightforward construction and analysis of the cascade de-excitation trees with inclusion of additional shake-off ejections of outer-shell electrons caused by the change of atomic core potential due to cascade transitions. The spectra of the cascade-produced electrons and photons emitted upon the decay of single vacancies in 1s1/2 to 4p3/2 subshells are calculated. For each initial vacancy, the energies absorbed by the silver atom itself, and those carried away by cascade electrons and photons, are calculated. Absorption of energy by the silver atom itself is only significant upon N- and M-shell ionization (49–66% and 18–36%, respectively), i.e. in the UV to soft X-ray range. After L- to N-ionization, most of the acquired energy is reemitted with cascade electrons, respective portions making 81–85% during L-ionization, 62–82% during M-ionization, and 34–51% during N-ionization. Reemission of energy with cascade photons is dominant after K-ionization (76%). When silver atoms are used as radiosensitizing agents in radiotherapy, cascade electrons play the principal role in the energy transfer to organism tissues. Due to small free paths in the organic medium, they give their energy to the environment in rather small volumes inside a particular cell where they are placed. As for the photons emitted after K-ionization, they transfer energy to the medium in much larger volumes, and with much smaller absorbed doses.

Wickramaratne K.M., Karki S.B., Ramezanipour F.

Purnakanti A., Lakshmi Y.K., Kumar S., Venkatesh R., Reddy M.S.

La0.67Ca0.33MnO3 manganite sample was synthesized using a sol–gel technique, and it was subsequently mixed with 1% of the additives Li2CO3, Bi2O3 and ZrO2, respectively. X-ray diffraction studies confirmed all the four samples were formed in single phase having an orthorhombic perovskite structure with the space group pnma. The estimated average grain size varies between 0.944 μm and 1.245 μm, and well-defined grains were observed in the additive samples with significant grain morphology in Li2CO3 additive, using morphological analysis. The magnetic and electrical behaviors of prepared samples were investigated in the temperature range (5–325 K) under constant applied magnetic field. The ferromagnetic to paramagnetic transition temperature (TC) was found to be more than 300 K and exhibiting 50% of ferromagnetic fraction at room temperature. The metal–insulator transition temperature (TP) is found to be in the neighborhood of the TC. The study expounds the role of 1% addition of additives: Li2CO3 acts as conduction barrier at the grain boundaries and hence an increase in the magnitude of resistivity, whereas Bi2O3, ZrO2 act as conduction channel at grain boundaries as a result the decrease in resistivity when compared with the pure sample. The ZrO2 additive sample exhibiting highest MR% includes extrinsic and intrinsic nature, whereas the Li2CO3 additive sample exhibiting extrinsic nature only. The conduction mechanism was explained in ferromagnetic metallic phase and paramagnetic insulator phase using electron–magnon scattering model and small polaron hopping model, respectively.

Yavna V., Shapovalov V., Okost M., Morozov A., Ermolov Y., Kochur A.

Subgrade is an important construction element of the railroad track. In the process of long-term operation, the subgrade is loaded by trains and exposed to natural climatic factors, such as wind and seismic loads, moisture caused by atmospheric precipitations and groundwater, exposure to positive and negative temperatures. At the same time, the subgrade must provide reliability and stable properties of the railway track because its renovations are the most expensive ones among those for the railway track in general. Due to this fact, national regulatory documents for the construction of the subgrade impose strict requirements on its deformity for the entire duration of modern railways operation. One of the ways to solve this problem on the stage of construction designing is computer predictive modelling of structural behavior that considers the changes of its elements and properties of construction materials under the long-term train impact taking into consideration the varying natural climatic factors. In this review, we analyze accumulated scientific and technical experience in formulating optimal approaches to the determination of initial data for computer simulation of repeated impact of the train loads for predicting railway track subgrade deformation considering engineering-geological conditions and natural climatic factors. We describe the stages of creating the subgrade computer modelling taking into account the analysis of trains load impact, the properties of model’s structural layers, and the change of soil properties under long-term loads.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

Abstract Cascade decays of single vacancies in K to O shells of the gold atom are simulated by straightforward construction and analysis of the cascade decay trees. Portions of energies a) absorbed by initially ionized Au atom, b) reemitted by cascade-produced electrons, and c) reemitted by cascade-produced photons are calculated with taking into account the shake-off processes caused by the change of atomic core potential during cascade transitions. Au atom absorbs noticeable amount of energy acquired in photoionization act only when ionized in its N and O shells, 33–45% and 41–54%, respectively. Except for the case of K-ionization, most of the energy is reemitted by cascade electrons: 57–64%, 77–85%, 55–67%, and 46–59% during the decay of vacancies in L, M, N, and O shells. Energies carried away by the cascade photons are only important for initial vacancies in K (89%) and L (29–39%) shells. Inclusion of the shake-off branches in the decay trees increase substantially their complexity, however it leads to comparatively small corrections to calculated portions of energy redistributed through channels a, b, and c. This supports earlier qualitative prediction of small possible effect of the SO processes on the cascades in heavy atoms.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

Abstract Final ion yields and mean final ion charges upon the cascade decay of single vacancies in the K, L, M, and N shells of atomic silver are calculated using the method of construction and analysis of the decay trees with accounting for the shake-offs caused by the change of atomic core potential due to cascade transitions. The shake-off effect on the final ion yields is found to be comparatively small, the largest increase of the mean final ion charge being 0.20e in the case of initial 2s vacancy. Total semi-relativistic Pauli–Fock energies of cascade-produced ionic configurations were used to calculate cascade transition energies, which made it possible to accurately account for the closing of some non-radiative transitions in multivacancy cascade configurations. For the transitions with overlapping multiplets of initial and final ionic configurations, only energetically allowed transitions between the multiplet components were counted when calculating mean transition energies and transitions branching ratios. Comparison of calculated charge spectra with those reported earlier by other authors demonstrated crucial importance of accurate calculation of transition energies and accounting for multiplet splitting in simulation of cascades in heavy atoms.

Chaynikov A.P., Kochur A.G., Dudenko A.I., Yavna V.A.

A method of straightforward construction and analysis of the cascade decay trees is applied to calculate photon and electron spectra emitted upon the cascade de-excitation of single inner-shell vacancies in the gold atom produced by photoionization. The energy acquired by the gold atom upon photoionization is split into the following channels: i) energy absorbed by the gold atom itself, ii) energy carried away by the cascade electrons, and iii) energy carried away by the cascade photons. The energies absorbed through channels i–iii are analyzed for the cascade decay of each single vacancy in O to K shells, and presented as functions of incident photon energies based on calculated partial photoionization cross sections. Energy reemitted through channels ii and iii in the cases of O-, N-, M-, L-, and K-ionization make, respectively, 47–60%, 55–69%, 85–89%, 94–96%, and 99% of the initially acquired energy. Cascade-produced electrons and photons eventually transfer their energy to the medium which lays the base for using gold-containing compounds and gold nanoparticles as radiosensitizing agents in radiotherapy. Cascade-produced electrons, as well as photoelectrons, are found to be the principal transmitters of energy to atoms of the environment in the vicinity of the sites of initial ionization. Their relative role in possible radiosensitizing effect is analyzed on the incident photon energy range of 0.01–1000 keV.

Явна В.А., Дуденко А.И., Кочур А.Г., Чайников А.П.

The probabilities of the formation of final ions produced by the cascade decays of vacancies in the K, L, M, N, and O shells of the gold atom are calculated. Simulation of the cascade decays of vacancies is performed by direct construction and analysis of decay trees using branching ratios and transition energies calculated in the Pauli–Fock approximation for multivacancy electron configurations arising in the course of the cascade decay. Accounting for additional monopole ejections of electrons (shake-off) accompanying the cascade transitions leads to a slight increase in the average charges of the final ions, by 0.15–0.23e. The largest relative increase in the calculated average charges of the final ions (by 3.6–3.9%) is observed upon the cascade decay of vacancies in 4p3/2, 4d3/2, and 4d5/2 subshells, and the smallest (by 0.8%) occurs in the decay of 4f-vacancy. Despite insignificant changes in the average ion charges, the structure of the charge spectra in some cases changes noticeably enough when additional electron ejections are taken into account. It is expected that in simulation of the cascade energy reemission processes when heavy atoms are used as radiosensitizers, the effect of accounting for shake-off processes will be insignificant.