Relaxation and Resonance Absorption

Ryogo Kubo, Morikazu Toda, Natsuki Hashitsume

David Liljequist

A simple demonstration of the effect of relaxation on a resonance absorption spectrum is described. The complexities involved in a formal theoretical treatment are avoided by employing a straightforward and intuitively obvious Monte Carlo simulation. Starting from first-order perturbation theory of resonance absorption, it is noted that the absorption spectrum is related to the Fourier transform of the time dependence of the perturbation and the absorbing oscillator. A semiclassical generalization of the time dependence of the oscillator to include fluctuating resonance frequencies gives a simple expression for the absorption spectrum in the presence of adiabatic relaxation. This expression is evaluated explicitly, using the Monte Carlo method to produce the required random-nature fluctuations.

E. H. Weinberg

Y. Ron Shen

The resonant scattering which is governed by transverse relaxation is physically different from absorption followed by emission which is affected by longitudinal relaxation. A number of physical examples are given.

Yury V. Kistenev

For atmospheric conditions, the relaxation matrix is characterized by both broadening of the absorption line and spatial variation of the frequency shift. The variations, adding to spatial variations of gas concentration, can cause specific peculiarities in effects of resonance interaction. Nonstationary refraction in a region of resonance interaction was shown to cause essential changing of the atmosphere transmission when propagation direction is changed. Analysis of the last group of phenomena for a case of constant resonance absorption gas concentration is presented in this paper. The analysis was carried out for a model of two-layer nonhomogeneous medium.