Relaxation cascade in solids: microscopic theory

The relaxation of an electron excited to the high energy region, is accompanied by the creation of various excitations (plasmons, quasi-particles, phonons). The stages of this many-body, non-stationary phenomenon (cascade) are described microscopically. The electron distribution function n(ɛ, t) and characteristic times for the whole energy range, are calculated. Received 7 February 2003 Published online 11 April 2003     

Transverse momenta of secondaries from 200 GeV/c proton-nucleus interactions

A study of 100 interactions, produced by secondary particles from 200 GeV/c proton interactions in nuclear emulsions, has been made to estimate the transverse momenta of the secondary particles. The data have been analysed by different methods of energy estimation and the weighted average values ofp _t have been compared as estimated from various methods. An average value ofp _t equal to 0.38 ± 0.03 GeV/c, in proton-nucleus interactions at 200 GeV/c, has been obtained from the production mechanism method.     

Mechanism Equivalence in Enzyme–Substrate Reactions: Distributed Differential Delay in Enzyme Kinetics

We consider single enzyme–substrate reaction mechanisms involving multiple complexes and demonstrate that these are equivalent to a distributed delay system without complexes. The distribution of the delay is determined by the number of intermediates and the relative sizes of the rates of the individual reaction mechanisms. We also consider the limit where there are a large number of intermediate complexes, and the conditions under which a number of known reaction mechanisms are equivalent. The present formalism brings forth new perspectives in the implementation of experimental techniques to rule out particular reaction mechanisms by studying the distribution of the delay between reactant mixing and product formation.     

Balance-equation approach to impact ionization induced by an intense terahertz radiation: Application to InAs/AlSb heterojunctions

We have extended the balance equations to account for conduction-valence interband impact ionization (II) process induced by an intense terahertz (THz) electromagnetic irradiation in semiconductors, and applied them to study the II effect on electron transport and electron-hole pair generation-recombination rate in THz-driven InAs/AlSb heterojunctions (HJ). As many as needed multiphoton channels are self-consistently taken into account for yielding a given accuracy. The time evolution of transport state including THz-radiation-induced II process are monitored in details by an extensive time-dependent analysis. Two different physical stages, the quasi-steady state and the complete steady-state, are clearly identified from the present calculations. Intersubband electron transfer rate and net electron-hole generation rate are derived as functions of the THz radiation strength E _ac for various radiation frequencies from f _ac = 0.42 to 6 THz at lattice temperatures T = 6 K. It's indicated that the THz radiation with a larger E _ac or a lower f _ac, has a stronger effect on electron transport and II process. Qualitative agreement is obtained between the calculated electron-hole generation rate and the available experimental data for InAs/AlSb HJ's at T = 6 K. Received 24 May 2002 / Received in final form 26 August 2002 Published online 31 October 2002 RID="a" ID="a"e-mail: jccao8@hotmail.com