THRESHOLD PHOTOELECTRON-SPECTROSCOPY OF HF

The high-resolution threshold photoelectron spectrum of the HF molecul e has been measured using pulsed field ionization after single-photon excitation by coherent vacuum ultra-violet radiation. The adiabatic io nization potential for HF was found to be 129422.4 +/- 1 cm-1. In cont rast to HCI, only small changes in total angular momentum of the ion c ore are observed. The experimental results show a preference for the F 1 spin-orbit component for both vibrational states of the ion, whereas the vibrational branching ratio was found to be similar to the relati ve intensities obtained from the Franck-Condon principle.