PENNING IONIZATION AND PHOTOIONIZATION ELECTRON SPECTROMETRY OF HYDROGEN-FLUORIDE

An electron spectrometric study has been performed on HF using metastable helium and neon atoms as well as helium and neon resonance photons. High-resolution electron spectra were obtained for a pure He(2(3)S) beam, a mixed He(2(1)S, 2(3)S) beam, a mixed Ne(3s, P-3(2), P-3(0)) beam, and for HeI and NeI VUV light. From the comparison of vibrational populations of HF+ (X 2PI(i), upsilon') and HF+ (A 2SIGMA+, upsilon') produced by He(2(3)S) metastables and HeI resonance photons, we conclude that there is only a slight perturbation of the HF(X 1SIGMA+) potential in He(2(3)S) Penning ionization; no perturbation is found for HF+(X 2PI(i), upsilon') formation from Ne(P-3(2,0)) metastable ionization of HF. For He (2(1)S) + HF the X- and A-ionic state vibrational peak shapes are substantially broader than in the He(2(3)S) + HF case pointing to an additional, charge exchanged interaction (He+ + HF-) in the entrance channel of the former system. The vibrational population found for NeI(alpha) photoionization of HF for formation of HF + (X 2PI(i), upsilon') is found to differ considerably from that for NeI(beta) photoionization and from the Franck-Condon factors for unperturbed HF(X 1SIGMA+) and HF+(X 2PI(i)) potentials suggesting the presence of an autoionizing superexcited state of HF in the energy vicinity of the NeI(alpha) resonance photons. The HF+(X) 2PI3/2:2PI1/2 fine-structure branching ratios vary significantly with the ionizing agent in a similar way as previously found in HCl and HBr.