Photoionization of gallium at 3d-4p and 4s-np (n=5,6) resonances

Abstract

The simplest atoms having nonspherical symmetry are those with a single p electron in a valence shell. Of these, the group IIIB elements are excellent examples. As such, they form test cases for photoionization from open-shell systems. Through photoelectron-spectroscopy techniques, we have examined both partial cross sections and angular-distribution parameters for autoionization corresponding to promotion of a 3d electron to the 4p shell of gallium. The resulting ${\mathrm{dp}}^2$ configuration gives rise to a complicated multiplet structure across which the angular-distribution parameter varies considerably. We have also looked at the simpler structure resulting from promotion of one s electron to an np level, n=5,6. For these cases, the multiplet structure is simpler, but the influence of the resonance on the cross section and the angular distribution is pronounced. For the 4s4p${(}^3$P)5p resonance we find a value of β=-1 at the cross-section minimum. No calculations have been performed for this system, so we attempt a qualitative interpretation of our results based on an angular-momentum-transfer analysis.