Predissociation dynamics of the hydroxyl radical (OH) based on a five-state spectroscopic model

Abstract

Multi-reference configuration interaction (MRCI) potential energy curves (PECs) and spin-orbit couplings for the X ${}^2\Pi$, A ${}^2{\Sigma }^{+}$, 1 ${}^2{\Sigma }^{-}$, 1 ${}^4{\Sigma }^{-}$, and 1 ${}^4\Pi$ states of OH are computed and refined against empirical energy levels and transitions to produce a spectroscopic model. Predissociation lifetimes are determined by discretising continuum states in the variational method nuclear motion calculation by restricting the calculation to finite range of internuclear separations. Varying this range give a series of avoided crossings between quasi-bound states associated with the A ${}^2{\Sigma }^{+}$ and continuum states, from which predissociation lifetimes are extracted. 424 quasi-bound A ${}^2{\Sigma }^{+}$ state rovibronic energy levels are analysed and 374 predissociation lifetimes are produced, offering good coverage of the predissociation region. Agreement with measured lifetimes is satisfactory and a majority of computed results were within experimental uncertainty. A previously unreported A ${}^2{\Sigma }^{+}$ state predissociation channel which goes via the X ${}^2\Pi$ is identified in the calculations. A python package, binslt, is produced to calculate predissociation lifetimes, associated line broadening parameters, and uncertainties from Duo *.states files is made available. The PECs and other curves from this work will be used to produce a rovibronic ExoMol linelist and temperature-dependent photodissociation cross sections for the hydroxyl radical.

14 Pages, 11 figures, 11 tables, 3 supplementary files. To be published in Journal of Chemical Physics

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• Three-states model for calculating the $X$-$X$ rovibrational transition intensities in hydroxyl radical