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

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 Bv 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: ωe, ωexe, ωeye, ωeze, Be, and αe. 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.