Auger Decay Studies of Core-Excited HBr by Angle-resolved Photoelectron Spectroscopy

Angle-resolved, two-dimensional photoelectron spectra of HBr, covering the Br $3d\to \sigma $* resonances, $3d\to $\textit{nl}$\lambda $ Rydberg resonances and the $3d\to \varepsilon l$ continuum, have been measured,. The two $3d_{5/2,3/2}\to \sigma $* resonances are separated for the first time and are found to be around 70.84 and 71.87 eV, respectively. The atomic Auger lines are measured and their angular distribution parameters $\beta $ calculated. Their intrinsic anisotropy parameters $\alpha _{2}$ are found similar to those of the corresponding normal Auger decay lines in the isoelectronic counterpart Kr. Resonant enhancements on the valence photolines from all the $3d$ resonances have been observed and found to have different effects on the angular distribution parameters $\beta $ of the photolines. The potential energy curves of the $\sigma $* state and the related dissociative molecular states are quantitatively predicted.