Аннотация:The hydroxyl radical OH is one of the first diatomic molecule discovered in the cold interstellar medium. The OH spectra is often observed in stellars, Sun, Earth and other planet atmospheres as well as a working body of a cosmic masers. It is also important intermediate product of high energy collisions and photodissociation.
To use the emission and absorbtion OH spectra in a diagnostic of high temperature enviroments the rovibronic term values and optical transition probabilities are required in a wide range of the excitation energy. It obviously means that all intramolecular interactions should be properly taken account in a global deperturbation analysis. It is not trivial to realize even for the lowest electronic states of OH since the strong competition between spin-orbit coupling, electronic-vibrational, electronic-rotational and ro-vibrational interactions is taking place. Moreover, the last two perturbations rapidly increase as the rotational excitation of the light OH molecule increases.
In this work we have studied options to improve the current deperturbation model based on the conventional band-by-band effective Hamiltonian approach [1] using the reduced coupled-channel (RCC) model [2] which explicitly accounts for spin-orbit, electronic-rotational and ro-vibrational interactions. It was found that taking into account for the 2-nd order mass-dependent non-adiabatic correction for both vibrational and rotational kinetic energy terms is crucially important for such light molecule as hydroxyl. Indeed, using this slightly modified version
of the RCC model [3], all experimental rotational levels belonging to the lowest v=0-2 vibrational levels of the ground state X2Π could be represented within the experimental uncertainty [4]. However, the RCC model still fails
to describe the higher vibrational levels with the appropriate spectroscopic accuracy.
The work was supported by the Russian Science Foundation (grant No. 22-23-00272,
https://rscf.ru/en/project/22-23-00272/).
References:
1. J.S.A. Brooke, P.F. Bernath, C.M. Western, C. Sneden, M. Afsar, G. Li, I.E. Gordon, JQSRT 168, 142 (2016).
2. S.V. Kozlov, E.A. Pazyuk, A.V. Stolyarov, Opt. Spectrosc. 125, 464 (2018).
3. S.V. Kozlov, E.A. Pazyuk, Opt.Spectrosc. 12, 1517 (2022).
4. T. Furtenbacher, S. T. Hegedus, J. Tennyson, A.G. Császár, PCCP 24, 19287 (2022).
