Contribution of incoherent effects to the orientation dependence of bremsstrahlung from rapid electrons in crystal

The bremsstrahlung cross section for relativistic electrons in a crystal is split into the sum of coherent and incoherent parts (the last is due to a thermal motion of atoms in the crystal). Although the spectrum of incoherent radiation in crystal is similar to one in amorphous medium, the incoherent radiation intensity could demonstrate substantial dependence on the crystal orientation due to the electrons' flux redistribution in the crystal. In the present paper we apply our method of the incoherent bremsstrahlung simulation developed earlier to interpretation of some recent experimental results obtained at the Mainz Microtron MAMI.Comment: VIII International Symposium "Radiation from Relativistic Electrons in Periodic Structures" (RREPS-09) Zvenigorod, Russia, September 7-11, 200

Dynamical Chaos and Level Splitting under the Channeling of the High Energy Positrons in [100] Direction of the Silicon Crystal

The motion of charged particles in a crystal in the axial channeling regime can be both regular and chaotic. The chaos in quantum case manifests itself in the statistical properties of the energy levels set. These properties have been studied previously for the electrons channeling along [110] direction of the silicon crystal, in the case when the classical motion was completely chaotic, as well as for the ones channeling along [100] direction, when the classical motion can be both regular and chaotic for the same energy depending on the initial conditions. Here we study the positrons channeling in [100] direction. This case is of special interest due to the substantial tunneling probability between dynamically isolated regular motion domains in the phase space. The interaction of the energy levels via tunneling distinctly changes the level spacing statistics. All transverse motion energy levels as well as corresponding stationary wave functions are computed numerically for the 30 GeV positrons channeling in [100] direction of the silicon crystal. The values of the matrix elements for the tunnel transitions are extractad from these data. These results confirm the chaos assistance for the tunneling and the level splitting. These values will be used in the further researches of the quantum chaos manifestations in the channeling phenomenon.Comment: Presented on the XIV International Symposium "Radiation from Relativistic Electrons in Periodic Structures", September 18-22, 2023, Tsaghkadzor, Armeni

Statistical properties of the transverse-motion energy levels for channeling electrons in a silicon crystal under dynamical chaos conditions

This paper studies the calculated energy levels of the transverse motion of relativistic electrons in the axial-channeling regime along the [100] direction of the silicon crystal which is described as motion in the smooth potential well. The nearest-level spacing distributions as well as the spectral rigidity are studied for the range of parameters where electron motion is chaotic within the classical limit. Both these characteristics demonstrate agreement with quantum-chaos-theory prediction

Positrons vs electrons channeling in silicon crystal: energy levels, wave functions and quantum chaos manifestations

The motion of fast electrons through the crystal during axial channeling could be regular and chaotic. The dynamical chaos in quantum systems manifests itself in both statistical properties of energy spectra and morphology of wave functions of the individual stationary states. In this report, we investigate the axial channeling of high and low energy electrons and positrons near direction of a silicon crysta

Splitting of the transverse-motion energy levels of positrons during channeling in the [100] direction of a silicon crystal

The motion of charged particles in the crystal can be both regular and chaotic. Within the quantum approach, chaos manifests itself in the statistical properties of the set of energy levels. The systems in which regions of regular motion are separated by that of chaotic motion in phase space are of special interest. The statistics of levels of these systems is greatly influenced by the possibility of tunneling between phase-space regions dynamically isolated from each othe

The investigation of quasi-characteristic radiation of electrons channeled along the charged axes in the crystals of zinc blende

For slight relativistic electrons moving along the main charged [100] and [110] axes in the crystals of zinc blende there was made a numerical calculation of the transverse energy levels and corresponding wave functions. It was done the calculation and the comparison of quasi-characteristic radiation spectra for these axe

Regular and chaotic motion domains in the channeling electron's phase space and mean level density for its transverse motion energy

The motion of charged particles in a crystal in the axial channeling regime can be both regular and chaotic. The chaos in quantum case manifests itself in the statistical properties of the energy levels set. These properties have been studied previously for the electrons channeling along direction of the silicon crystal, in the case when the classical motion was completely chaotic. It is demonstrated that the level spacing distribution for both electrons and positrons can be better described by Berry-Robnik distribution than by both Wigner (completely chaotic case) or Poisson (completely regular case) distribution

Рост пурпурных серных бактерий Thiocapsa sp. Shira_1 при низких температурах, характерных для хемоклина озера Шира

Forecasting the abundance of phototrophic sulfur bacteria in lakes is very important because 1) these bacteria are major consumers of hydrogen sulfide, and 2) fossil carotenoids of these bacteria are retrospective biomarkers of limnological conditions. Therefore, understanding the factors controlling the dynamics of the abundance of phototrophic sulfur bacteria in a lake is necessary both for the prediction of hydrogen sulfide content and for paleo-limnological reconstruction. Based on long-term monitoring of the abundance of purple sulfur bacteria (PSB) in the saline meromictic Lake Shira (South Siberia, Khakassia), we proposed a hypothesis that relatively small changes in water temperature in the cold deep chemocline affect the PSB abundance in the lake. We tested this hypothesis experimentally. The purple sulfur bacterium Thiocapsa sp. Shira_1 (Chromatiaceae) from Lake Shira (South Siberia, Russia) was grown on a sulfide-containing synthetic medium under anoxic conditions in batch culture at low temperatures, from -1ºC to +8ºC, which were similar to in situ temperatures observed in the chemocline of Lake Shira. The cell growth rate at +8ºC was similar to the growth rate at room temperature, whereas there was no growth at -1ºC and +5ºC. Therefore, the variations in the biomass of purple sulfur bacteria (PSB) observed in Lake Shira could be caused by variations in chemocline temperature. The high correlation between chemocline temperature and PSB biomass supported this conclusionПрогноз динамики численности фототрофных серных бактерий в природных стратифицированных водоемах признан важной задачей. Во-первых, данная группа бактерий – основной потребитель сероводорода, который является токсическим и бальнеологическим компонентом. Во-вторых, каротиноиды фототрофных серных бактерий, захороненные в донных отложениях, используются в качестве биомаркеров прошлых состояний озера. Таким образом, знание факторов, контролирующих активность фототрофных серных бактерий, необходимо как для прогноза концентрации сероводорода, так и для палеоклиматических реконструкций. На основе многолетних наблюдений за динамикой численности пурпурных серных бактерий (ПСБ) в соленом меромиктическом озере Шира (юг Сибири, Хакасия) нами была выдвинута гипотеза о том, что небольшие вариации температуры воды в холодном и глубоком хемоклине озера влияют на численность ПСБ. Для проверки этой гипотезы нами исследован рост штамма пурпурных серных бактерий Thiocapsa sp. Shira_1 из меромиктического соленого озера Шира в периодической культуре при температурах от минус 1 до 8 °С, характерных для зоны хемоклина данного озера. Бактерий выращивали при постоянном освещении в анаэробных условиях на синтетической среде с добавлением сероводорода. Показано, что рост данного штамма при 8 °С не отличался от такового при комнатной температуре, тогда как при температурах минус 1 и 5 °С достоверный рост отсутствовал. Результаты эксперимента свидетельствуют, что повышение температуры в зоне хемоклина озера до 8 °С является фактором, способствующим увеличению численности популяции этих бактерий в озере, что согласуется с многолетними наблюдениям