Theoretical study of the low-lying doublet and quartet electronic states of 7Li16O molecule including spin-orbit coupling effect and a new limit to the adiabatic ionization energy

The potential energy curves of ⁷Li¹⁶O molecule for energies below 50,000 cm⁻¹ have been investigated. All doublet and quartet electronic states considered here are studied at the CASSCF/icMRCI(Q) level of theory associated with the aug-cc-pV5Z basis set. Within this range of energies, analytical representations are proposed. To evaluate the accuracy of these functional forms, a novel set of spectroscopic parameters have been derived. Transition probability parameters as the Franck–Condon factors and Einstein A coefficients of certain vibronic emissions from the $A^2{\Sigma }^{+}-X^2\Pi ,2^2\Pi -X^2\Pi$, and $2^2\Pi -A^2{\Sigma }^{+}$band systems are reported. It was found that rotationless radiative lifetimes of the order of milliseconds are determined for A-X and C-X bands. Overall, our results transition probabilities suggest that these vibronic emissions are weak and, therefore, difficult to measure in spectroscopy experiments. Additionally, we obtained an adiabatic ionization energy value of 68,002 cm⁻¹.