GRECP/MRD-CI calculations of the spin-orbit splitting in
the ground state of Tl and of the spectroscopic properties
of TlH

Authors: A.V.Titov, N.S.Mosyagin, A.B.Alekseyev, R.J.Buenker
Comments: 20 pages, latex, no figures, more comutational details are available at at this http URL
Subj-class: Chemical Physics

The generalized relativistic effective core potential (GRECP) approach is employed in
the framework of multireference single- and double-excitation configuration interaction
(MRD-CI) method to calculate the spin-orbit (SO) splitting in the $^2P^o$ ground
state of the Tl atom and spectroscopic constants for the $0^+$ ground state of TlH.
The 21-electron GRECP for Tl is used and the outer core 5s and 5p pseudospinors
are frozen with the help of the level shift technique. The spin-orbit selection scheme
with respect to relativistic multireference states and the corresponding code are
developed and applied in the calculations. In this procedure both correlation and
spin-orbit interactions are taken into account. A [4,4,4,3,2] basis set is optimized for
the Tl atom and employed in the TlH calculations. Very good agreement is found for
the equilibrium distance, vibrational frequency, and dissociation energy of the TlH
ground state ($R_e=1.870 \AA, \omega_e=1420 cm^{-1}, D_e=2.049 eV$) as
compared with the experimental data ($R_e=1.868 \AA, \omega_e=1391 cm^{-1}, D_e=2.06 eV$).

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