SPIN-POLARIZATION IN HBR - COMPARISON BETWEEN THEORY AND EXPERIMENT

Measurements of the electron spin polarization parameter A have been p erformed for HBr in the energy region between the two ionization thres holds, (II3/2)-I-2 and (II1/2)-I-2. Using the multichannel quantum def ect theory and formulas derived for the spin parameters in intermediat e coupling between Hund's cases (a) and (e), calculations for both the cross section and the A parameter have been performed. It is shown th at the values of A for each Rydberg resonance change with n, following the change from Hund's case (a) to case (e). In the approximations us ed in this paper, no simple relation between the sign of A and the val ue of J(+), the rotational angular momentum of the ion core, was found . Values for the calculated angular asymmetry parameter beta and the s pin polarization parameter xi are also presented. Since our calculatio ns reproduced only part of the observed resonances, and since the meas urements of the A parameter have been performed in relatively narrow e nergy regions, one could not perform an extensive comparison between t heory and experiment. However, some of the peculiarities of the behavi or of the A parameter observed experimentally have been qualitatively reproduced by our calculations. (C) 1998 American Institute of Physics .