RESONANCE AND INTERFERENCE PHENOMENA IN THE PHOTIONISATION OF A HYDROGEN-ATOM IN A UNIFORM ELECTRIC-FIELD .3. COMPARISON WITH RECENT EXPERIMENTAL AND THEORETICAL RESULTS

The recent experimental and theoretical works on the Stark photoionisation spectrum of the hydrogen atom are analysed and compared with the results of the semiclassical approach developed in the preceding papers of the present series. It is shown that the observed cross section structure is described by the semiclassical theory without any modifications. Thus the experiments confirm the principal advantage of the semiclassical theory: it is uniform both in photoelectron energy and the electric field strength. In particular, the measured Stark photodetachment cross sections are reproduced well by simple analytical formulae. The shape of the resonance profiles is described by Fano parametrisation. Its criticism by Harmin (1985) is shown to be unjustified. Lorentz parametrisation with the energy-dependent width proposed by Harmin suffers from serious disadvantages. Fano parametrisation with account for rapid variation of the cross section background reproduces all the characteristic features of the profiles observed in experiments by Bergeman et al. (1984). The semiclassical results agree well with the recent numerical calculations for resonances lying above the ionisation threshold. The approximate expressions for the resonance widths describe the experimental results well.