On the use of the semiclassical approximation for the calculation of oscillator strengths and photoionization cross sections

The semiclassical formula for the radial integrals of bound-bound dipole transitions derived in a previous paper is modified for obtaining more accurate estimates and extending to bound-free transitions. The possibility of these is due to the special definition of the mean value of energy generalizing that of the previous paper. It is shown that the definition is optimal in the sense of the best agreement between semiclassical and exact quantum mechanical results in a limiting case. Matching with the corresponding expression for free-free transitions is also obtained. Good agreement with experiment and more accurate calculations is found. (author)