Ab initio study of R-dependent behavior of the hyperfine structure parameters for the (1)1,3Σ+ states of LiRb and LiCs

Abstract Diagonal a 3 Σ 1 + - a 3 Σ 1 + and off–diagonal X 1 Σ 0 + + - a 3 Σ 0 - + magnetic hyperfine structure (HFS) matrix elements were calculated ab initio for the LiRb and LiCs molecules in a wide range of internuclear distances using the multi–reference Fock space coupled clusters method with generalized relativistic effective core potentials to describe the four–component valence wavefunctions near the nuclei. At large distances, both HFS functions vary little, though they may fluctuate by as much as 12 to 24 % in the intermediate range. The plateau exhibited by the a 3 Σ 1 + - a 3 Σ 1 + HFS function at 4–5 A, could be attributed to pronounced spin–orbit coupling of the intersecting a 3 Σ + and b 3 Π states.