Pub Date : 2021-09-27DOI: 10.33581/2520-2243-2021-3-49-61
V. Tikhomirov
The problem of high-energy charged particle motion in the field of atomic strings and planes of oriented crystals, widely applied to control large accelerator beams and generate intense gamma radiation, is addressed. Following the previously developed theory of channeled particles incoherent scattering by crystal atom nuclei, we consider here the same by crystal atom electrons. The theory developed takes into consideration all the effects of momentum transfer between fast particles and electrons of atoms in a crystal in the range from the nuclear radius up to the many inter-atomic distances. The theory also includes the temperature-dependent Debye – Waller factor, as well as both the atomic form factors and scattering function, evaluated with the detail consideration of atomic structure. All the modifications of electron scattering in crystals are reduced to the value of the effective minimum momentum transfer, which by an order of value exceeds that one, related with the Bethe – Bloch mean atomic energy. Substituting this quantity to the expression for the mean square of the scattering angle of a classically moving particle makes it possible to compare the scattering by electrons and nuclei, while its joint use with the Rutherford cross section allows for the correct simulations of the planar channeling of positively charged particles in the thickest crystals, supposed to be used for the beam extraction from high energy accelerators, measurement of electromagnetic characteristics of short-living particles and development of intense narrow-band X-ray and gamma radiation sources based on crystal undulators.
{"title":"Incoherent ultrarelativistic channeling particle scattering by electrons","authors":"V. Tikhomirov","doi":"10.33581/2520-2243-2021-3-49-61","DOIUrl":"https://doi.org/10.33581/2520-2243-2021-3-49-61","url":null,"abstract":"The problem of high-energy charged particle motion in the field of atomic strings and planes of oriented crystals, widely applied to control large accelerator beams and generate intense gamma radiation, is addressed. Following the previously developed theory of channeled particles incoherent scattering by crystal atom nuclei, we consider here the same by crystal atom electrons. The theory developed takes into consideration all the effects of momentum transfer between fast particles and electrons of atoms in a crystal in the range from the nuclear radius up to the many inter-atomic distances. The theory also includes the temperature-dependent Debye – Waller factor, as well as both the atomic form factors and scattering function, evaluated with the detail consideration of atomic structure. All the modifications of electron scattering in crystals are reduced to the value of the effective minimum momentum transfer, which by an order of value exceeds that one, related with the Bethe – Bloch mean atomic energy. Substituting this quantity to the expression for the mean square of the scattering angle of a classically moving particle makes it possible to compare the scattering by electrons and nuclei, while its joint use with the Rutherford cross section allows for the correct simulations of the planar channeling of positively charged particles in the thickest crystals, supposed to be used for the beam extraction from high energy accelerators, measurement of electromagnetic characteristics of short-living particles and development of intense narrow-band X-ray and gamma radiation sources based on crystal undulators.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79641901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-20DOI: 10.33581/2520-2243-2021-2-4-14
A. Maskevich
We have investigated the spectral properties of a new benzothiazole dye – a thioflavin T derivative – 3-sulfopropyl-5-methoxy-2-[3-(3,5-diethyl-2-benzothiazolidene)-1-propienyl]-benzothiazolium (Th-C11). Based on quantum-chemical calculations, it is shown that the molecule in the ground state has a flat structure. In an excited state, the minimum energy corresponds to a twisted conformation, in which the aromatic fragments are arranged orthogonally. Since the twisted state is non-fluorescent, the transition to this state (torsion relaxation) is a quenching process. Th-C11 dye exhibits the properties of a fluorescent molecular rotor. As a result of experimental studies, it was found that torsion relaxation of molecular fragments is the main process that determines the strong dependence of the quantum yield and the duration of fluorescence decay on the viscosity of the solvent. A characteristic feature of this dye is the sensitivity of the fluorescence parameters – the quantum yield, the decay duration and the position of the spectrum not only to the viscosity, but also to the polarity of the medium. The paper also explains the dependence of the position of the absorption and fluorescence spectra on the polarity and viscosity of the solvent as a result of the manifestation of the processes of torsion and solvation relaxation of the chromophore and solvent molecules.
{"title":"Fluorescent properties anionic derivative of thioflavin T","authors":"A. Maskevich","doi":"10.33581/2520-2243-2021-2-4-14","DOIUrl":"https://doi.org/10.33581/2520-2243-2021-2-4-14","url":null,"abstract":"We have investigated the spectral properties of a new benzothiazole dye – a thioflavin T derivative – 3-sulfopropyl-5-methoxy-2-[3-(3,5-diethyl-2-benzothiazolidene)-1-propienyl]-benzothiazolium (Th-C11). Based on quantum-chemical calculations, it is shown that the molecule in the ground state has a flat structure. In an excited state, the minimum energy corresponds to a twisted conformation, in which the aromatic fragments are arranged orthogonally. Since the twisted state is non-fluorescent, the transition to this state (torsion relaxation) is a quenching process. Th-C11 dye exhibits the properties of a fluorescent molecular rotor. As a result of experimental studies, it was found that torsion relaxation of molecular fragments is the main process that determines the strong dependence of the quantum yield and the duration of fluorescence decay on the viscosity of the solvent. A characteristic feature of this dye is the sensitivity of the fluorescence parameters – the quantum yield, the decay duration and the position of the spectrum not only to the viscosity, but also to the polarity of the medium. The paper also explains the dependence of the position of the absorption and fluorescence spectra on the polarity and viscosity of the solvent as a result of the manifestation of the processes of torsion and solvation relaxation of the chromophore and solvent molecules.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"102 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74826528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.33581/2520-2243-2021-2-34-43
A. Kholmetskii, T. Yarman, O. Yarman, Metin Arik
We discuss the results of modern Mössbauer experiments in a rotating system, which show the presence of an extra energy shift between the emitted and absorbed resonant radiation in addition to the relativistic energy shift of the resonant lines due to the time dilation effect in the co-rotating source and absorber with different radial coordinates. We analyse the available attempts to explain the origin of the extra energy shift, which include some extensions of special theory of relativity with hypothesis about the existence of limited acceleration in nature, with hypothesis about a so-called «time-dependent Doppler effect», as well as in the framework of the general theory of relativity under re-analysis of the metric effects in the rotating system, which is focused to the problem of correct synchronisation of clocks in a rotating system with a laboratory clock. We show that all such attempts remain unsuccessful until the moment, and we indicate possible ways of solving this problem, which should combine metric effects in rotating systems with quantum mechanical description of resonant nuclei confined in crystal cells.
{"title":"Mössbauer experiments in a rotating system and physical interpretation of their results","authors":"A. Kholmetskii, T. Yarman, O. Yarman, Metin Arik","doi":"10.33581/2520-2243-2021-2-34-43","DOIUrl":"https://doi.org/10.33581/2520-2243-2021-2-34-43","url":null,"abstract":"We discuss the results of modern Mössbauer experiments in a rotating system, which show the presence of an extra energy shift between the emitted and absorbed resonant radiation in addition to the relativistic energy shift of the resonant lines due to the time dilation effect in the co-rotating source and absorber with different radial coordinates. We analyse the available attempts to explain the origin of the extra energy shift, which include some extensions of special theory of relativity with hypothesis about the existence of limited acceleration in nature, with hypothesis about a so-called «time-dependent Doppler effect», as well as in the framework of the general theory of relativity under re-analysis of the metric effects in the rotating system, which is focused to the problem of correct synchronisation of clocks in a rotating system with a laboratory clock. We show that all such attempts remain unsuccessful until the moment, and we indicate possible ways of solving this problem, which should combine metric effects in rotating systems with quantum mechanical description of resonant nuclei confined in crystal cells.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87887483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-07DOI: 10.33581/2520-2243-2020-2-70-77
O. Gusakova, Yuliya M. Shulya, H. Skibinskaya, V. Ankudinov
The paper presents the results of comparing the microstructure of alloys of the Al – Ge system of eutectic and near- eutectic compositions synthesized at melt cooling rates of 102 and 105 K/s. It was shown by scanning electron microscopy that at a cooling rate of 102 K/s, crystallization starts with grain growth of the excess component and ends with a eutectic reaction. The microstructure of bulk samples is characterized by large inclusions of aluminum and germanium and heterogeneity of composition at sample cross section. The size reduction of phase particles of alloys of the Al – Ge system of eutectic and near-eutectic compositions is achieved using high-speed solidification. It is shown that the cooling rate of the melt increase causes size reduction of phase particles by 2–3 orders. The layering of the microstructure of the cross section of rapidly solidified foils was also revealed, and a mechanism for its formation was proposed taking into account changes in the solidification conditions over the thickness of the foil. Using differential scanning calorimetry, it was shown that an increase in the cooling rate provides a narrowing of the melting temperature range and an increase in the melting rate.
{"title":"Effect of melt cooling rate on the microstructure and thermal properties of Al – Ge alloy","authors":"O. Gusakova, Yuliya M. Shulya, H. Skibinskaya, V. Ankudinov","doi":"10.33581/2520-2243-2020-2-70-77","DOIUrl":"https://doi.org/10.33581/2520-2243-2020-2-70-77","url":null,"abstract":"The paper presents the results of comparing the microstructure of alloys of the Al – Ge system of eutectic and near- eutectic compositions synthesized at melt cooling rates of 102 and 105 K/s. It was shown by scanning electron microscopy that at a cooling rate of 102 K/s, crystallization starts with grain growth of the excess component and ends with a eutectic reaction. The microstructure of bulk samples is characterized by large inclusions of aluminum and germanium and heterogeneity of composition at sample cross section. The size reduction of phase particles of alloys of the Al – Ge system of eutectic and near-eutectic compositions is achieved using high-speed solidification. It is shown that the cooling rate of the melt increase causes size reduction of phase particles by 2–3 orders. The layering of the microstructure of the cross section of rapidly solidified foils was also revealed, and a mechanism for its formation was proposed taking into account changes in the solidification conditions over the thickness of the foil. Using differential scanning calorimetry, it was shown that an increase in the cooling rate provides a narrowing of the melting temperature range and an increase in the melting rate.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88195106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-07DOI: 10.33581/2520-2243-2020-2-78-85
R. Shulyakovsky, A. Gribowsky, A. Garkun, M. Nevmerzhitsky, A. Shaplov, D. A. Shohonov
Instantons are non-trivial solutions of classical Euclidean equations of motion with a finite action. They provide stationary phase points in the path integral for tunnel amplitude between two topologically distinct vacua. It make them useful in many applications of quantum theory, especially for describing the wave function of systems with a degenerate vacua in the framework of the path integrals formalism. Our goal is to introduce the current situation about research on instantons and prepare for experiments. In this paper we give a review of instanton effects in quantum theory. We find in stanton solutions in some quantum mechanical problems, namely, in the problems of the one-dimensional motion of a particle in two-well and periodic potentials. We describe known instantons in quantum field theory that arise, in particular, in the two-dimensional Abelian Higgs model and in SU(2) Yang – Mills gauge fields. We find instanton solutions of two-dimensional scalar field models with sine-Gordon and double-well potentials in a limited spatial volume. We show that accounting of instantons significantly changes the form of the Yukawa potential for the sine-Gordon model in two dimensions.
瞬子是具有有限作用的经典欧几里得运动方程的非平凡解。它们在两个拓扑不同的真空之间的隧道振幅的路径积分中提供了固定相位点。这使得它们在量子理论的许多应用中非常有用，特别是在路径积分形式主义的框架中描述具有简并真空的系统的波函数。我们的目的是介绍有关瞬子的研究现状，并为实验做准备。本文综述了量子理论中的瞬子效应。我们在一些量子力学问题中，即粒子在两阱和周期势中的一维运动问题中，找到了斯坦顿解。我们描述了量子场论中出现的已知瞬子，特别是在二维阿贝尔希格斯模型和SU(2) Yang - Mills规范场中。我们在有限的空间体积中找到了具有正弦戈登势和双阱势的二维标量场模型的瞬解。我们表明，计算瞬时子显著地改变了二维正弦戈登模型的汤川势的形式。
{"title":"Classical instanton solutions in quantum field theory","authors":"R. Shulyakovsky, A. Gribowsky, A. Garkun, M. Nevmerzhitsky, A. Shaplov, D. A. Shohonov","doi":"10.33581/2520-2243-2020-2-78-85","DOIUrl":"https://doi.org/10.33581/2520-2243-2020-2-78-85","url":null,"abstract":"Instantons are non-trivial solutions of classical Euclidean equations of motion with a finite action. They provide stationary phase points in the path integral for tunnel amplitude between two topologically distinct vacua. It make them useful in many applications of quantum theory, especially for describing the wave function of systems with a degenerate vacua in the framework of the path integrals formalism. Our goal is to introduce the current situation about research on instantons and prepare for experiments. In this paper we give a review of instanton effects in quantum theory. We find in stanton solutions in some quantum mechanical problems, namely, in the problems of the one-dimensional motion of a particle in two-well and periodic potentials. We describe known instantons in quantum field theory that arise, in particular, in the two-dimensional Abelian Higgs model and in SU(2) Yang – Mills gauge fields. We find instanton solutions of two-dimensional scalar field models with sine-Gordon and double-well potentials in a limited spatial volume. We show that accounting of instantons significantly changes the form of the Yukawa potential for the sine-Gordon model in two dimensions.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"149 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82276917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-04DOI: 10.33581/2520-2243-2020-2-28-41
N. Poklonski, S. A. Vyrko, A. N. Dzeraviaha
In the work the dependence of the thermal ionization energy of hydrogen-like donors and acceptors on their concentration in n- and p-type semiconductors is analyzed analytically and numerically. The impurity concentrations and temperatures at which the semiconductors are on the insulator side of the concentration insulator – metal phase transition (Mott transition) are considered. It is assumed that impurities in the crystal are distributed randomly (according to Poisson), and their energy levels are distributed normally (according to Gauss). In the quasi-classical approximation, it is shown, for the first time, that the decrease in the ionization energy of impurities mainly occurs due to the joint manifestation of two reasons. Firstly, from the excited states of electrically neutral impurities, a quasicontinuous band of allowed energy values is formed for c-band electrons in an n-type crystal (or for v-band holes in a p-type crystal). This reduces the energy required for the thermally activated transition of electron from the donor to the c-band (for the transition of the hole from the acceptor to the v-band). Secondly, from the ground (unexcited) states of impurities a classical impurity band is formed, the width of which at low temperatures is determined only by the concentration of impurity ions. In moderately compensated semiconductors (when the ratio of the concentration of minority impurities to the concentration of majority impurities is less than 50 %) the Fermi level is located closer to the edge of the band of allowed energy values than the middle of the impurity band, that issue reduces thermal ionization energy of impurities from states in the vicinity of the Fermi level (transition of electron from a donor to the c-band, or hole from an acceptor to the v-band). Previously, these two causes of decrease in the thermal ionization energy due to increase in the concentration of impurities were considered separately. The results of calculations according to the proposed formulas are quantitatively agree with the known experimental data for a number of semiconductor materials (germanium, silicon, diamond, gallium arsenide and phosphide, silicon carbide, zinc selenide) with a moderate compensation ratio.
{"title":"Thermal ionization energy of hydrogen-like impurities in semiconductor materials","authors":"N. Poklonski, S. A. Vyrko, A. N. Dzeraviaha","doi":"10.33581/2520-2243-2020-2-28-41","DOIUrl":"https://doi.org/10.33581/2520-2243-2020-2-28-41","url":null,"abstract":"In the work the dependence of the thermal ionization energy of hydrogen-like donors and acceptors on their concentration in n- and p-type semiconductors is analyzed analytically and numerically. The impurity concentrations and temperatures at which the semiconductors are on the insulator side of the concentration insulator – metal phase transition (Mott transition) are considered. It is assumed that impurities in the crystal are distributed randomly (according to Poisson), and their energy levels are distributed normally (according to Gauss). In the quasi-classical approximation, it is shown, for the first time, that the decrease in the ionization energy of impurities mainly occurs due to the joint manifestation of two reasons. Firstly, from the excited states of electrically neutral impurities, a quasicontinuous band of allowed energy values is formed for c-band electrons in an n-type crystal (or for v-band holes in a p-type crystal). This reduces the energy required for the thermally activated transition of electron from the donor to the c-band (for the transition of the hole from the acceptor to the v-band). Secondly, from the ground (unexcited) states of impurities a classical impurity band is formed, the width of which at low temperatures is determined only by the concentration of impurity ions. In moderately compensated semiconductors (when the ratio of the concentration of minority impurities to the concentration of majority impurities is less than 50 %) the Fermi level is located closer to the edge of the band of allowed energy values than the middle of the impurity band, that issue reduces thermal ionization energy of impurities from states in the vicinity of the Fermi level (transition of electron from a donor to the c-band, or hole from an acceptor to the v-band). Previously, these two causes of decrease in the thermal ionization energy due to increase in the concentration of impurities were considered separately. The results of calculations according to the proposed formulas are quantitatively agree with the known experimental data for a number of semiconductor materials (germanium, silicon, diamond, gallium arsenide and phosphide, silicon carbide, zinc selenide) with a moderate compensation ratio.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78700888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-02DOI: 10.33581/2520-2243-2020-2-19-27
N. Belko, M. Samtsov, A. Lugovski
Aggregation process of a symmetrical cationic indotricarbocyanine dye in aqueous medium was studied. It was shown that self-assembled H*-aggregates with an absorption peak at 514 nm as well as J-aggregates with an absorption peak at 777 nm can be obtained. Both of the aggregate types are non-fluorescent. High concentration of a desired aggregate type can be obtained and stabilized by changing ionic strength and pH of the solution. At ionic strength of 170 mmol/L and pH 7.4 J-aggregates are stable. Decreasing pH as well as ionic strength leads to demise of J-aggregates and concomitant formation of H*-aggregates. Increasing temperature leads to a faster H*-aggregate formation. The type of aggregates can be changed by heating and subsequent cooling of the solution. An organic compound forming both H*- and J-aggregates has never been observed before. The fact that the H*- and J-bands are narrow, the shift between them is significant, the J-band is located in the far-red spectral region, and the type of aggregates can be controlled makes these objects promising for future applications.
{"title":"Controlling H*- and J-aggregation of an indotricarbocyanine dye in aqueous solutions of inorganic salts","authors":"N. Belko, M. Samtsov, A. Lugovski","doi":"10.33581/2520-2243-2020-2-19-27","DOIUrl":"https://doi.org/10.33581/2520-2243-2020-2-19-27","url":null,"abstract":"Aggregation process of a symmetrical cationic indotricarbocyanine dye in aqueous medium was studied. It was shown that self-assembled H*-aggregates with an absorption peak at 514 nm as well as J-aggregates with an absorption peak at 777 nm can be obtained. Both of the aggregate types are non-fluorescent. High concentration of a desired aggregate type can be obtained and stabilized by changing ionic strength and pH of the solution. At ionic strength of 170 mmol/L and pH 7.4 J-aggregates are stable. Decreasing pH as well as ionic strength leads to demise of J-aggregates and concomitant formation of H*-aggregates. Increasing temperature leads to a faster H*-aggregate formation. The type of aggregates can be changed by heating and subsequent cooling of the solution. An organic compound forming both H*- and J-aggregates has never been observed before. The fact that the H*- and J-bands are narrow, the shift between them is significant, the J-band is located in the far-red spectral region, and the type of aggregates can be controlled makes these objects promising for future applications.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80264927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-01DOI: 10.33581/2520-2243-2020-2-4-9
K. V. Kozadaev
The paper demonstrates an approach to modeling the thermophysical parameters of vapor in an ablative silver jet propagating at atmospheric pressure. The proposed semi-empirical model is based on the modification of the Anisimov – Luk’yanchuk model taking into account the Zeldovich – Raiser dynamic condensation theory. Such process of dynamic condensation of spherical (or semi-spherical) ablative jets can also be graphically represented as passing in the expanding vapor-plasma cloud of the three spatial concentric spherical waves from the periphery to the center of cloud. There are «saturation» wave (corresponding to the moment of crossing the Poisson adiabate with saturation adiabate at the phase diagram of vapor), wave of nuclear «etching» (the moment of greatest supercooling of vapor in the jet) and the «quenching» wave (stabilization of the condensation degree of the vapor in the jet). Due to the revision of a number of basements of the Anisimov – Luk’yanchuk model, it was possible to offer an adequate description of thermodynamic processes occurring at normal atmospheric gas pressure.
{"title":"Dynamics of thermophysical parameters of silver ablation jets at atmospheric pressure","authors":"K. V. Kozadaev","doi":"10.33581/2520-2243-2020-2-4-9","DOIUrl":"https://doi.org/10.33581/2520-2243-2020-2-4-9","url":null,"abstract":"The paper demonstrates an approach to modeling the thermophysical parameters of vapor in an ablative silver jet propagating at atmospheric pressure. The proposed semi-empirical model is based on the modification of the Anisimov – Luk’yanchuk model taking into account the Zeldovich – Raiser dynamic condensation theory. Such process of dynamic condensation of spherical (or semi-spherical) ablative jets can also be graphically represented as passing in the expanding vapor-plasma cloud of the three spatial concentric spherical waves from the periphery to the center of cloud. There are «saturation» wave (corresponding to the moment of crossing the Poisson adiabate with saturation adiabate at the phase diagram of vapor), wave of nuclear «etching» (the moment of greatest supercooling of vapor in the jet) and the «quenching» wave (stabilization of the condensation degree of the vapor in the jet). Due to the revision of a number of basements of the Anisimov – Luk’yanchuk model, it was possible to offer an adequate description of thermodynamic processes occurring at normal atmospheric gas pressure.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78371250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-31DOI: 10.33581/2520-2243-2020-1-41-53
N. Poklonski, A. N. Dzeraviaha, S. A. Vyrko, A. I. Kavaleu
The study of semiconductor materials with point radiation defects of the crystal structure in three charge states (–1), (0), (+1) is important for determining the conditions of their radiation resistance under the influence of gamma rays, fast electrons, etc. Such defects are self-sufficient to ensure electrical neutrality of the material under conditions of ionization equilibrium, that issue determines the radiation resistance of materials. In silicon and diamond crystals, such irradiation-induced defects during their accumulation stabilize the Fermi level in the vicinity of one third of the band gap from the top of the valence band. The purpose of the work is an analytical description of the stationary hopping electron transfer in a semiconductor, taking into account the joint migration of both the single electrons and the pairs of electrons over these triple-charged defects. A crystalline semiconductor is considered as a matrix containing immobile point defects of one sort in the prevailing concentration. For the first time in the drift-diffusion approximation, a phenomenological theory is constructed of coexisting migration of both the single electrons (transitions from the charge state (–1) to state (0) and from the state (0) to state (+1)), and the electron pairs (transitions from the state (–1) to state (+1)) by means of their hopping between such defects when an external stationary electric field is applied to the semiconductor. In the linear approximation, analytical expressions are obtained for the screening length of a static electric field and the length of the hopping diffusion of electrons migrating via such defects. It is shown that the additional contribution of the hopping transport of electron pairs leads to a decrease in the screening length and also changes the diffusion length.
{"title":"Migration of electrons via triple-charged defects of crystal matrix","authors":"N. Poklonski, A. N. Dzeraviaha, S. A. Vyrko, A. I. Kavaleu","doi":"10.33581/2520-2243-2020-1-41-53","DOIUrl":"https://doi.org/10.33581/2520-2243-2020-1-41-53","url":null,"abstract":"The study of semiconductor materials with point radiation defects of the crystal structure in three charge states (–1), (0), (+1) is important for determining the conditions of their radiation resistance under the influence of gamma rays, fast electrons, etc. Such defects are self-sufficient to ensure electrical neutrality of the material under conditions of ionization equilibrium, that issue determines the radiation resistance of materials. In silicon and diamond crystals, such irradiation-induced defects during their accumulation stabilize the Fermi level in the vicinity of one third of the band gap from the top of the valence band. The purpose of the work is an analytical description of the stationary hopping electron transfer in a semiconductor, taking into account the joint migration of both the single electrons and the pairs of electrons over these triple-charged defects. A crystalline semiconductor is considered as a matrix containing immobile point defects of one sort in the prevailing concentration. For the first time in the drift-diffusion approximation, a phenomenological theory is constructed of coexisting migration of both the single electrons (transitions from the charge state (–1) to state (0) and from the state (0) to state (+1)), and the electron pairs (transitions from the state (–1) to state (+1)) by means of their hopping between such defects when an external stationary electric field is applied to the semiconductor. In the linear approximation, analytical expressions are obtained for the screening length of a static electric field and the length of the hopping diffusion of electrons migrating via such defects. It is shown that the additional contribution of the hopping transport of electron pairs leads to a decrease in the screening length and also changes the diffusion length.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"182 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77732298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-31DOI: 10.33581/2520-2243-2020-1-67-72
V. Shepelevich, D. Zernitsa
Microstructure of rapidly solidified eutectic alloy foil Sn – 8.8 wt. % Zn was studied. The alloy foil consists of solid solutions of zinc and tin. Dark equiaxed dispersed precipitates of zinc solid solution are uniformly interspersed in the matrix of tin solid solution. The parameters of the microstructure were determined. The average chord of a random secant at the sections of precipitates of a solid solution of zinc is 0.33 mm, and the specific interface surface is 0.81 mm–1. The precipitations of the tin solid solution have a microcrystalline structure. Specific surface of high angle boundaries less than 1 mm–1. The texture of the precipitates of solid solutions of tin and zinc in the foil was studied, and the pole densities of the diffraction lines of these phases are presented. The tin solid solution has the texture (100), and the zinc solid solution has the (0001) texture, which is explained by the predominant growth of grains, in which the crystalline planes of (100) tin and (0001) zinc are most closely packed and perpendicular to the heat flux. Eutectic alloy Sn – 8.8 wt. % Zn is in an unstable state. Annealing the foil causes the dissolution of small and coarsening of large particles of zinc solid solution, as well as the decomposition of a supersaturated tin solid solution. These processes cause an enlargement of the microstructure: an increase in the average particle size (dZn) of a solid solution of zinc and its volume fraction (VZn), a decrease in the specific surface (S ) of interphase boundaries.
{"title":"The structure of rapidly solidified foil of the eutectic Sn – 8.8 wt. % Zn alloy","authors":"V. Shepelevich, D. Zernitsa","doi":"10.33581/2520-2243-2020-1-67-72","DOIUrl":"https://doi.org/10.33581/2520-2243-2020-1-67-72","url":null,"abstract":"Microstructure of rapidly solidified eutectic alloy foil Sn – 8.8 wt. % Zn was studied. The alloy foil consists of solid solutions of zinc and tin. Dark equiaxed dispersed precipitates of zinc solid solution are uniformly interspersed in the matrix of tin solid solution. The parameters of the microstructure were determined. The average chord of a random secant at the sections of precipitates of a solid solution of zinc is 0.33 mm, and the specific interface surface is 0.81 mm–1. The precipitations of the tin solid solution have a microcrystalline structure. Specific surface of high angle boundaries less than 1 mm–1. The texture of the precipitates of solid solutions of tin and zinc in the foil was studied, and the pole densities of the diffraction lines of these phases are presented. The tin solid solution has the texture (100), and the zinc solid solution has the (0001) texture, which is explained by the predominant growth of grains, in which the crystalline planes of (100) tin and (0001) zinc are most closely packed and perpendicular to the heat flux. Eutectic alloy Sn – 8.8 wt. % Zn is in an unstable state. Annealing the foil causes the dissolution of small and coarsening of large particles of zinc solid solution, as well as the decomposition of a supersaturated tin solid solution. These processes cause an enlargement of the microstructure: an increase in the average particle size (dZn) of a solid solution of zinc and its volume fraction (VZn), a decrease in the specific surface (S ) of interphase boundaries.","PeriodicalId":17264,"journal":{"name":"Journal of the Belarusian State University. Physics","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75619477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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