Место издания:Publishing House of IAO SB RAS Tomsk
Первая страница:138
Последняя страница:138
Аннотация:The rates of molecular dissociation induced by light are important parameters of various atmospheric and astrophysical models. In particular, solar photons are believed to be the main source of destruction of molecules formed by the meteoroid impact on the planets and moons with rarified exospheres. For sodium, as the most important spectroscopic tracer, some correlations were found between the meteor showers and appearance of the high kinetic energy atoms [1]. Thermodynamic models point out that NaO is one of the main products of the cooled impact-produced cloud [2]. Its photolysis cross sections at selected wavelength were measured in the laboratory and solar photolysis rate is estimated [3]. Thus, NaO molecule becomes an attractive model for the first-principle studies.
Potential energy curves, transition dipole moments, spin-orbit (SO) and angular coupling matrix elements for the states correlating to three lowest dissociation limits were calculated ab initio using the multi-reference configuration interaction method. It was found that several pathways may contribute to the photolysis at the wavelengths up to 200 nm, where intense solar radiation produces the products with high kinetic energies. The photodissociation rates from the thermally populated rovibronic levels of the ground X2 and the closely-lying (Te < 2000 cm-1) excited A2+ states were estimated for the spectral region in the framework of both quasi-static and quantum adiabatic approaches. First, the spin-allowed transitions to the repulsive B2Σ и (3)2П states, converging to the first and second dissociation limits, were considered. Then the indirect photodissociation via the intermediate “shelf-like” bound 22П state, which is coupled with the B2Σ by SO interaction, was accounted for. The non-adiabatic effects in the rovibronic energies and wave functions of the X2 and A2+ were estimated as well. Preliminary results indicate the non-Boltzmann population of the initial rovibronic X2 and A2+ states.
This research was supported by RFBR grant No. 15-03-003302a.