Аннотация:Accurate potential energy curves for the alkali metal – rare gas collision pairs are required to predict and optimize the scaling characteristics of optically pumped alkali metal vapor laser systems [1]. We performed high-level ab initio calculations to construct relativistic interatomic potentials for the lowest electronic states of the Rb-Rg (Rg=He, Ne, Ar) dimers.
Inner electron shells of Rb atom (1-3s, 2-3p, 3d) are replaced by the shape-consistent relativistic two-component pseudopotential (PP)2, leaving subvalence (4sp) and valence shells for explicit treatment. The PP was fitted to reproduce both the wave function outside the core and excitation spectrum of the valence 5s electron. The corresponding valence basis set is adjusted for reproducing the atomic 2S1/2, 2P1/2, 2P3/2 polarizabilities. Electronic structure of rare gas atoms (He, Ne, Ar) is described at the all-electron level using quadruple-zeta quality basis set with additional polarization functions. Correlation problem is solved by the relativistic multiconfigurational Fock-space coupled-cluster method using the Kramers-restricted Dirac-Hartree-Fock solution for RbRg+ ion as the vacuum state. All 9 electrons of Rb atom and valence 8 (for Ne, Ar) or 2 (for He) electrons of Rg atom are correlated while Ne/Ar inner [1s2]/[1s22s22p6] shells are frozen. The active space is spanned by the first 4 virtual Kramers pairs. The fully relativistic potential energy curves (PECs) are obtained for the ground (i)Ω=(1)1/2 and first excited (i)Ω=(2,3)1/2, (1)3/2 molecular states in a wide range of internuclear distance.
To explore the impact of the spin-orbit coupling effect on the Rb-Ar excited states we alternatively used for Rb atom the energy-consistent 9-valence-electron PP3. The electronic energies and wave functions are obtained in the framework of multireference configuration interaction method. The resulting energies of the B2Σ+ and A2Π states are diagonalized analytically with the calculated diagonal and off-diagonal spin-orbit matrix elements to build quasi-relativistic PECs for the corresponding Ω=1/2 and 3/2 states. Calculations are performed with the DIRAC15 and MOLPRO2010 packages. The work is supported by the RFBR under Grant No. 16-03-00766.
References
[1] W.F. Krupke, R.J. Beach, V.K. Kanz, S.A. Payne, J.T. Early, Proc. SPIE 5448, High-Power Laser Ablation V, 7, September 20, 2004
[2] N.S. Mosyagin, A.V. Zaitsevskii, A.V. Titov, Int. Rev. At. Mol. Phys. 1, 63, 2010
[3] I.S. Lim, P. Schwerdtfeger, B. Metz, H. Stoll, J. Chem. Phys. 122, 104103, 2005