Rotationally resolved vacuum ultraviolet pulsed field ionization- photoelectron vibrational bands for H D+ (X g+2, v+ =0-20)

Abstract

The authors have obtained rotationally resolved vacuum ultraviolet pulsed field ionization-photoelectron (vuv-PFI-PE) spectrum of HD in the photon energy range of 15.29-18.11 eV, covering the ionization transitions H D+ (X g+2, v+ =0-21, N+) HD (X g+1, v″ =0, J″). The assignment of rotational transitions resolved in the vuv-PFI-PE vibrational bands for H D+ (X g+2, v+ =0-20) and their simulation using the Buckingham-Orr-Sichel (BOS) model are presented. Rotational branches corresponding to the ΔN= N+ - J″ =0, ±1, ±2, ±3, and ±4 transitions are observed in the vuv-PFI-PE spectrum of HD. The BOS simulation shows that the perturbation of vuv-PFI-PE rotational line intensities due to near resonance autoionization is very minor at v+ 5 and decreases as v+ is increased. Thus, the rotationally resolved PFI-PE bands for H D+ (v+ 5) presented here provide reliable estimates of state-to-state cross sections for direct photoionization of HD, while the rotationally resolved PFI-PE bands for H D+ (v+ <5) are useful data for fundamental understanding of the near resonance autoionizing mechanism. On the basis of the rovibrational assignment of the vuv-PFI-PE bands, the ionization energies for the formation of H D+ (X g+2, v+ =0-20, N+) from HD (X g+1, v″ =0, J″) and the vibrational constants (ωe, ωe e, ωe ye, and ωe ze), the rotational constants (Be and αe), the vibrational energy spacings, and the dissociation energy for H D+ (X g+2) are determined. As expected, these values are found to be in excellent agreement with high level theoretical predictions. © 2007 American Institute of Physics.