Nonperturbative method for core–valence correlation in pseudopotential calculations: Application to the Rb2 and Cs2 molecules

Abstract

The core–valence correlation is introduced into ab initio relativistic pseudopotential calculations by modifying the existing core polarization potential. The salient feature of the method presented here is the use of an l-dependent cutoff parameter (which is related to spherical harmonic functions) for solving the multicenter integrals over the 1/r4 - and r/r3 -type operators. The method is tested on the Rb2 and Cs2 molecules considered as two valence-electron problems. Reliable results for the molecular spectroscopic constants (Re, Te, De, and ωe ) are obtained for the ground state and the lowest excited states. Deviation from the experimental values ranges from 0.05 to 0.1 Å for Re, seldom exceeds 2 cm−1 for ωe, and is of the order of 100 cm−1 for De for most of the excited states.

Ground- and excited-state properties of the polar and paramagnetic RbSr molecule: A comparative study

“…It is based on the representation of the Rb + and Sr 2+ ionic cores by relativistic effective core potential (ECP) complemented with core polarization potential (CPP) simulating core-valence correlation along the lines developed by Müller and Meyer [52,53] and Foucrault et al [54].These effective potentials involve semi-empirical parameters (reported in Ref. [18]) which are chosen to reproduce the energies of the lowest s, p and d levels of the Rb and Sr + one-valence-electron systems.…”

Efficient formation of strongly bound ultracold caesium molecules by photoassociation with tunnelling

“…The metastable a 3 Σ + u (6S 1/2 + 6S 1/2 ) state is represented by the potential curve of [28], matched beyond 20a 0 to the standard asymptotic expansion C n /R n (n = 6, 8, 10), with C n coefficients taken from [29]. The repulsive wall of the potential is slightly changed in order to reproduce a large and positive scattering length [30].…”

Experimental investigation of the Cs2 a Σ3u+ triplet ground state: Multiparameter Morse long range potential analysis and molecular constants

“…1 Theoretical calculations indicate that the a 3 ⌺ u + state has a shallow well. [2][3][4][5][6] Weickenmeier and co-workers 7,8 determined the R e , e , and D e molecular parameters through hyperfine-induced X 1 ⌺ g + ϳa 3 ⌺ u + mixing. Using photoassociation of cold atoms, levels near the dissociation limit have also been probed.…”