Optical phonon scattering and theory of magneto-polarons in a quantum cascade laser in a strong magnetic field

We report a theoretical study of the carrier relaxation in a quantum cascade laser (QCL) subjected to a strong magnetic field. Both the alloy (GaInAs) disorder effects and the Frohlich interaction are taken into account when the electron energy differences are tuned to the longitudinal optical (LO) phonon energy. In the weak electron-phonon coupling regime, a Fermi's golden rule computation of LO phonon scattering rates shows a very fast non-radiative relaxation channel for the alloy broadened Landau levels (LL's). In the strong electron-phonon coupling regime, we use a magneto-polaron formalism and compute the electron survival probabilities in the upper LL's with including increasing numbers of LO phonon modes for a large number of alloy disorder configurations. Our results predict a nonexponential decay of the upper level population once electrons are injected in this state.Comment: 10 pages, 23 figure

Density-matrix theory of the optical dynamics and transport in quantum cascade structures: The role of coherence

The impact of coherence on the nonlinear optical response and stationary transport is studied in quantum cascade laser structures. Nonequilibrium effects such as pump-probe signals, the spatio-temporally resolved electron density evolution, and the subband population dynamics (Rabi flopping) as well as the stationary current characteristics are investigated within a microscopic density-matrix approach. Focusing on the stationary current and the recently observed gain oscillations, it is found that the inclusion of coherence leads to observable coherent effects in opposite parameter regimes regarding the relation between the level broadening and the tunnel coupling across the main injection barrier. This shows that coherence plays a complementary role in stationary transport and nonlinear optical dynamics in the sense that it leads to measurable effects in opposite regimes. For this reason, a fully coherent consideration of such nonequilibrium structures is necessary to describe the combined optical and transport propertiesComment: 14 pages, 11 figures; final versio

Numerical Simulation of Multicomponent Ion Beam from Ion Sources

A program library for numerical simulation of a multicomponent charged particle beam from ion sources is presented. The library is aimed for simulation of high current, low energy multicomponent ion beam from ion source through beamline and realized under the Windows user interface for the IBM PC. It is used for simulation and optimization of beam dynamics and based on successive and consistent application of two methods: the momentum method of distribution function (RMS technique) and particle in cell method. The library has been used to simulate and optimize the transportation of tantalum ion beam from the laser ion source (CERN) and calcium ion beam from the ECR ion source (JINR, Dubna)

Perturbative fragmentation

The Berger model of perturbative fragmentation of quarks to pions is improved by providing an absolute normalization and keeping all terms in a (1-z) expansion, which makes the calculation valid at all values of fractional pion momentum z. We also replace the nonrelativistic wave function of a loosely bound pion by the more realistic procedure of projecting to the light-cone pion wave function, which in turn is taken from well known models. The full calculation does not confirm the (1-z)^2 behavior of the fragmentation function (FF) predicted in for $z>0.5$, and only works at very large z>0.95, where it is in reasonable agreement with phenomenological FFs. Otherwise, we observe quite a different z-dependence which grossly underestimates data at smaller z. The disagreement is reduced after the addition of pions from decays of light vector mesons, but still remains considerable. The process dependent higher twist terms are also calculated exactly and found to be important at large z and/or pT.Comment: 10 pages, 8 figure

Cyclotron resonance in a two-dimensional electron gas with long-range randomness

We show that the the cyclotron resonance in a two-dimensional electron gas has non-trivial properties if the correlation length of the disorder is larger than the de Broglie wavelength: (a) the lineshape assumes three different forms in strong, intermediate, and weak magnetic fields (b) at the transition from the intermediate to the weak fields the linewidth suddenly collapses due to an explosive growth in the fraction of electrons with a diffusive-type dynamics.Comment: A few typos correcte

Large Rapidity Gap Processes in Proton-Nucleus Collisions

The cross sections for a variety of channels of proton-nucleus interaction associated with large gaps in rapidity are calculated within the Glauber-Gribov theory. We found inelastic shadowing corrections to be dramatically enhanced for such events. We employ the light-cone dipole formalism which allows to calculate the inelastic corrections to all orders of the multiple interaction. Although Gribov corrections are known to make nuclear matter more transparent, we demonstrate that in some instances they lead to an opaqueness. Numerical calculations are performed for the energies of the HERA-B experiment, and the RHIC-LHC colliders.Comment: 19 page

Клинический случай поражения молнией

Atmospheric electricity damage as a result of lightning strike is a relatively rare condition in intensive care medicine, however it can be accompanied by high mortality and serious complications in the majority of survived patients.The objective was to demonstrate a clinical case of lightning injury and discussion of diagnostic and treatment aspects in this condition.Materials and Methods. 18-yr old patient was delivered to hospital after lightning strike. She lost consciousness, there was no breathing for a short time, and the witnesses provided artificial respiration and external cardiac compressions. On admission, the signs of shock were present in parallel with dopamine infusion, the skin was pale-grey and cold, with traces of thermal damage according to the type of contact with metal of various localization on the neck, scalp, front surface of the chest and abdominal wall, in the groin, on the left foot. The patient was hospitalized to ICU, therapeutic and diagnostic measures were started. We revealed decompensated lactic acidosis, biochemical signs of myocardial and muscle damage. The infusion therapy, analgesics, antibiotics, proton pump inhibitors, anticoagulants were administered. During the therapy in the first 6 hours, the signs of shock were attenuated, in 4 days, the patient was transferred to traumatological department in a stable state. After the transfer from the ICU, hearing decline as well as pain and sensory disturbances in the left foot are persisting.Conclusion. An integrated approach is required in the diagnosis, treatment, and rehabilitation of patients with lightning injury.Поражение атмосферным электричеством в результате удара молнии – состояние, достаточно редко встречающееся в реанимационной практике; вместе с тем, оно сопровождается высокой смертностью и серьезными осложнениями у значительной части выживших пациентов.Цель – демонстрация клинического наблюдения поражения атмосферным электричеством и обсуждение аспектов диагностики и лечения данной патологии.Материалы и методы. Пациентка 18 лет доставлена в стационар после поражения молнией на берегу. Отмечалась потеря сознания, кратковременно отсутствовало дыхание, свидетели происшествия проводили искусственное дыхание и наружный массаж сердца. При поступлении – признаки шока на фоне инфузии допамина, кожный покров бледно-серый, холодный, следы термического повреждения по типу соприкосновения с металлом различной локализации на шее, волосистой части головы, передней поверхности грудной клетки, брюшной стенке, в паховой области, на левой стопе. Госпитализирована в ОРИТ, начат комплекс мер диагностики и интенсивной терапии. Выявлены декомпенсированный метаболический ацидоз, биохимические признаки повреждения миокарда и мышечной ткани. Назначены инфузионная терапия, анальгетики, антибиотики, блокаторы протонной помпы, антикоагулянты. На фоне проводимого лечения в первые 6 часов явления шока купированы, через 4 суток в стабильном состоянии переведена в травматологическое отделение. После перевода из ОРИТ сохраняются нарушения слуха, боль и нарушения чувствительности в левой стопе.Заключение. Необходим комплексный подход в диагностике, лечении, реабилитации пациентов с поражением атмосферным электричеством