Free-Bound and Bound-Bound Radiative Transitions in an Intense Laser Field (U)

摘要

The transition rates for free-bound and bound-bound radiative absorption and emission in an intense laser field have been calculated. In the approximations used here, the rates may be represented by the product of two functions. One function, which contains all the details of the atomic structure, is independent of the laser field. The other function contains all the corrections caused by the intense laser field. The calculations were done using first-order perturbation theory to describe the effects of the intense laser field on the bound state levels and using a low-frequency approximation for the laser field. It is shown that both these approximations are quite good for the states and laser intensities of interest. The intense field-correction factor for the rate of bound-free transitions for electrons with a Boltzmann distribution of energies has been calculated. Numerical results for the correction factor for the Boltzmann case are presented. For typical laser fusion parameters, the correction factor, which is the ratio of the thermal free-bound emission rate in the intense field to the rate at zero field, can be quite significant. The major effect of the strong field on the bound-bound rate is to increase the width of the lines. Since the line width is a function of the laser field strength, this effect may be used to measure the laser field at various positions in a plasma. (ERA citation 06:004276)