The low-lying electronic states of BeI: Accounting for spin–orbit effects on the energetic profile characterization and molecular properties

Abstract All electronic states correlating with the two lowest Λ + S and the four lowest Ω dissociation channels of BeI are characterized at the CASSCF/MRCI level of theory with quintuple-zeta basis sets. Spin–orbit interactions modify significantly the potential energy curves in regions of curve crossings and avoided crossings, and explain the scarcity of spectroscopic data. Trends in energetic and molecular properties are discussed for BeF, BeCl, BeBr, and BeI. For the A 1 1/2(II)–X 1/2(I) and A 2 3/2(I)–X 1/2(I) band systems, transition moments, transition probabilities, and Franck–Condon factors were computed; radiative and tunneling lifetimes completed the characterization of these states.