ИСТИНА

The complex universal approach for calculation of the binary broadening of metal atoms spectral lines by buffer noble gas atoms is presented [1]. The approach is based on utilizing the modified Buckingham type analytic potential for the description of interatomic interaction. The parameters of this potential for the particular atomic radiative transition in the target atom and a particular perturbing atom, which determine its behavior at small interatomic distances, are found by fitting the potential curves, obtained for the case under consideration by ab initio quantum chemical calculations. The Van der Waals part of this potential is calculated using both ab initio modeling and the perturbation theory in the molecular basis. The latter allows to get more universal expressions than ab initio methods. The parameterized modified Buckingham type potential for the particular atomic radiative transition of a target atom and a particular perturbing atom is then used for calculations of the total line profile in the framework of the Unified Frank Condon Theory (UFCT). The first basic step in generating UFCT profile is the derivation of its impact limit. It is done in the semiclassical approximation with account of strong Coriolis coupling between the degenerate quasimolecular electronic states. As the impact frequency range corresponds to distant collisions, only the explicit Van der Waals part of the potential is used. Then since the main contribution is given by large values of angular momenta (correspondingly by large internuclear distances) the rectilinear trajectory of the colliding particles can be assumed, and it is possible to neglect coupling between atomic states with different projections of the atomic angular momentum on the axis, normal to the collision plane. This allows to get explicit analytical expressions for the impact line width [1]. The outer from impact range of frequency detunings is described by the UFCT expression, splitting the variation of impact parameters in two regions. In the first region, which is close to the turning point, the trajectory is constructed taking into account short range character of the potential and using the Takayanagi approximation. In the second region of larger impact parameters the trajectories can be considered as rectilinear. Moreover, it is assumed that the quasimolecular dipole moment of the radiative transition varies very slowly versus internuclear distance. So, it could be put as constant, factored out and canceled during normalization of the profile. The further study of the reduced Frank-Condon factor versus detuning allows establishing qualitative properties of the profile in the asymptotic red and blue wings, as well as the appearance of satellites [1]. And at last this knowledge of asymptotic behavior of the profile gives possibility of the total profile representation in a more simple approximate way on the basis of Van der Waals broadening, introducing general receipts for the characteristic frequency cut-offs for the red and blue wings [1]. REFERENCES [1] A.V. Demura, S.Ya. Umanskii, A.V. Scherbinin, A.V. Zaitsevskii, G.V. Demchenko, V.A. Astapenko, B.V. Potapkin, Evaluation of Van der Waals Broadening Data, IRAMP, 2012, accepted for publication