Spectral shape of a signal in light-induced diffusive pulling (pushing) of particles into a light beam

摘要

We study theoretically how the dependences of transport collision frequencies nu(i), collision broadening gamma and collision shift Delta of the levels on the velocity upsilon of resonant particles influence lightinduced diffusive pulling (pushing) ( LDP) effects in the framework of a generalised model of strong collisions in the case of velocitydependent collision rates ( so-called kangaroo model). It is found that allowance for the dependences ni( u), g( u) and D( u) does not change the spectral shape of an LDP signal. In particular, in the case of low-intensity radiation, the spectral dependence of the LDP signal coincides with the absorption line shape. It is shown that the magnitude of the LDP effect is proportional to the difference between the diffusion coefficients of particles in the excited and ground states. It is found that the spectral anomalies previously predicted in the LDP effect [Gel'mukhanov F.Kh. JETP Lett., 55, 214 ( 1992)] for an idealised model of the Lorentz gas ( the limiting case of heavy buffer particles), which arise due to the dependences nu(i)( u), gamma( upsilon) and Delta(upsilon), are typical only for this gas. At a realistic ratio of the masses of absorbing and buffer particles, spectral anomalies do not occur in the LDP effect.