Rotationally resolved photoelectron spectroscopy of n-H2, p-H2, HD, and D2

Abstract

The 584 Å photoelectron spectra of n‐H₂, p‐H₂, HD, and D₂ were recorded at a resolution of 11 meV FWHM using a supersonic molecular beam source. Spectra were taken at several stagnation temperatures and pressures in order to vary the rotational population distribution in the beam with a corresponding variation in the relative intensities of the rotational transitions. Many of the Q‐branch components were resolved for the first time. ΔG(v+1/2) and B_v values were measured for all observed vibrational states of H⁺₂, HD⁺, and D⁺₂ and were used to determined the ionic vibrational and rotational constants: ω_e, ω_ex_e, ω_ey_e, ω_ez_e, B_e, and α_e. The results represent a substantial improvement over previous experimental determinations and were found to be consistent with the available theoretical rotation‐vibration energy levels. The measurement of the intensity distribution of photoelectrons as a function of vibrational states yielded photoionization cross sections which were in good agreement with the theoretical values calculated by O′Niel and Reinhardt.