Rotational and fine structure of open-shell molecules in nearly degenerate electronic states. II. Interpretation of experimentally determined interstate coupling parameters of alkoxy radicals.

Abstract

Rotationally and fine-structure resolved B̃←X̃ laser-induced fluorescence (LIF) spectra of alkoxy radicals have been simulated with a "coupled two-states model" [J. Liu, J. Chem. Phys. 148, 124112 (2018)], in which the nearly degenerate X̃ and à states are considered together. These two electronic states are separated by the "difference potential" and coupled by the spin-orbit (SO) interaction and the Coriolis interaction. Molecular constants determined in fitting the LIF spectra using the coupled two-states model provide quantitative insight into the SO and Coriolis interactions, as well as other intramolecular dynamics, including the pseudo-Jahn-Teller effect. The spectroscopic model also allows semi-quantitative prediction of effective spin-rotation constants using molecular geometry and SO constants, which can be calculated ab initio with considerable accuracy. The dependence of fit values of molecular constants on the size and conformation of alkoxy radicals is discussed.