THRESHOLD PHOTOELECTRON-SPECTROSCOPY OF CL-2 AND BR-2 UP TO 35 EV

We have investigated the threshold photoelectron spectra of Cl-2 and B r-2 over the energy range from the onset of ionization up to 35 eV, us ing synchrotron radiation and employing a penetrating-field electron s pectrometer. The near-zero kinetic energy electron spectra in the vale nce ionization region reveal resolved vibrational structure in the dir ect formation of all valence ionization states. In addition, extended vibrational structure is found in the Franck-Condon gap region between the X (2) Pi(g,i) and A (2) Pi(u,i) systems that is indicative of the presence of autoionizing states. Analysis of the vibrational structur e contained in these band systems has generated improved spectroscopic constants. Extensive vibrational structure in the A (2) Pi(u,i) band system of Br-2(+) has been observed from both direct ionization and au toionization processes, enabling us to define the band origin of the l ower spin-orbit component. Energy perturbations are found in the lower vibrational bands (nu' = 0-7) in the Br-2(+)(A (2) Pi(u,3/2)) subsyst em. In the higher energy region studied, band structures related to co re ion and satellite ion state formation have been found in both halog en systems.