Soviet Physics Journal

, Volume 24, Issue 10, pp 967–970 | Cite as

Coherence of two-level systems and relaxation

  • M. M. Al'perin
  • Ya. D. Klubis


The relaxation of a two-level system interacting with radiation is studied using the method of coherent states. A solution of the equation for the quasiprobability density function is presented in two extreme cases of high and low photon field temperatures. In the first case, the equation has the form of a purely diffusion equation, and from the point of view of a spin interpretation, defines Brownian motion of a magnetic moment on a spherical surface. The second case leads to an equation of the general Fokker-Planck type, in which both diffusion and a systematic term are present. The results of an investigation of spontaneous emission of a system containing a large number of particles, using the quasiclassical approximation, are presented. In this approximation, a Gaussian distribution with a variable variance, whose center moves along a classical trajectory, is obtained for the quasiprobability distribution.


Radiation Coherence Density Function Brownian Motion Field Temperature 
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Copyright information

© Plenum Publishing Corporation 1982

Authors and Affiliations

  • M. M. Al'perin
    • 1
  • Ya. D. Klubis
    • 1
  1. 1.K. D. Ushinskii Pedagogical InstituteOdessa

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