BROADENING AND COLLISIONAL RELAXATION OF THE POTASSIUM 5P-2 LEVEL PERTURBED BY RARE-GASES - COMPARISON OF QUANTAL CALCULATIONS TO SEMI-CLASSICAL AND EXPERIMENTAL RESULTS

The broadening and shift constants of the K 404.4, 404.7 nm doublet and the depolarisation cross sections of the 52P level perturbed by the rare gases are studied. The broadening and shift by helium, argon, neon and xenon have been measured. Calculations of all the collisional cross sections by a purely quantal method have been performed for helium. A mixed quantum-semiclassical method has been used for argon and xenon. Comparisons of quantum and coupled semiclassical calculations for helium indicate marked quantum and trajectory effects below 10 au. However the broadening and shift results agree within a few per cent due to the small relative weight of the short impact parameters. Much larger discrepancies appear for the other cross sections (up to 70%). Except for neon, the experimental results for broadening and shift verify quite well the theoretical predictions especially for the broadening. In particular the different broadening of the two lines is generally well predicted.