Rotationally resolved vacuum ultraviolet pulsed field ionization-photoelectron vibrational bands for HD+(X 2Σg+,v+=0–20).

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 HD+(X 2Σg+,v+=0–21,N+)←HD(X 1Σg+,v″=0,J″). The assignment of rotational transitions resolved in the vuv-PFI-PE vibrational bands for HD+(X 2Σg+,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 HD+(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 HD+(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 HD+(X 2Σg+,v+=0–20,N+) from HD(X 1Σg+,v″=0,J″) and the vibrational constants (ωe, ωeχe, ωeye, and ωeze), the rotational constants (Be and αe), the vibrational energy spacings, and the dissociation energy for HD+(X 2Σg+) are determined. As expected, these values are found to be in excellent agreement with high level theoretical predictions. [ABSTRACT FROM AUTHOR]