ИСТИНА

Relevance. Matrix isolation is a method for investigating intractable, unstable and highly reac- tive species by encapsulating them within transparent, inert, solid medium at low temperatures. However, the utility of matrix isolation lies far beyond that. For instance, 1 S1–1 P1 atomic tran- sition of Ba atom, which, upon isolation in Xe matrix splits into several unique adsorption and corresponding emission bands, is used to monitor the rate of ββ0ν decay of 136 Xe, which is tied to the mass of electronic neutrino [1]. As such, thorough understanding of the Ba@Xe fluorescence is required for the accurate ββ0ν half-life to be obtained. Theoretical interpretation of the Ba@Xe emission spectra however, is lacking, partly because of the complications related to the treatment of matrix isolated (1 P1)Ba. Next, rare gas matrices can be used to trap molecules, radicals and single atoms. As matrix- isolated atoms have distinct and sharp thresholds for thermal diffusion, they can be activated separately, selectively inducing specific chemical reactions and allowing the synthesis of a number of otherwise unobtainable species and materials. There are however, several open questions related to the atomic diffusion in rare gas matrices. Atoms of one element can have several temperature thresholds, the nature of which is not always fully understood, despite the venerable amount of experimental research. The least understood are the atoms with non-zero electronic angular momenta, among which are very important interstellar reagents and intermediates, such as atomic carbon and oxygen. Despite being of similar mass and size with their Periodic Table neighbours, they have wildly different properties, which are not reproduced by the simulations. Two aforementioned applications, in addition to several others, would greatly benefit from the accurate and efficient approach of modeling P state atoms isolated in rare gas matrixes.