Theoretical Study on the Structure and Dissociation Mechanism of Electronic Excited States of Nitrosyl Bromide Molecules.

High-level ab initio calculations have been presented on nitrosyl bromide, BrNO, which are performed by the internally contracted explicitly correlated multireference configuration interaction (icMRCI-F12) method with Davidson correction. A total of 17 electronic states of BrNO from the ground state to the excited states at energy below 7 eV have been investigated. The energies and transitions of the states have been obtained, along with potential energy curves along the Br-N-O angle and the N-Br and N-O bond lengths. The photodissociation mechanism of the excited state involved in the UV-vis energy region has been discussed based on our calculation results. Our study would be of value to understand the interaction and dynamics of the electronic excited states and thus the photochemical processes of the BrNO molecules.