Simulation of photoelectron and electronic spectra of small molecules

In this contribution, a description is given of the application of high-level ab initio calculations and Franck-Condon analysis to study some photoelectron and electronic spectra, where there were uncertainties in their assignments. The spectra chosen are the He I photoelectron spectrum of BrO2and the single vibrational level (SVL) dispersed fluorescence spectra of AlCN and AlNC. With suitable ab initio calculations and subsequent spectral simulations, assignments of these spectra can now be made. In addition, the iterative Franck-Condon analysis (IFCA) procedure was also applied to some of these spectra to derive excited and ionic state geometries. In the investigation of the He I photoelectron spectrum observed when O(3P) reacted with Br2(1Σg+) calculations were performed on the low-lying triplet states of both BrOBr and BrBrO and their low-lying cationic quartet states for the first time. It was found that there are a number of weakly bound triplet radical-radical states and quartet radical-cation states for both BrOBr and BrBrO.