Permanent electric dipoles in B 1Π and D 1Π states of NaRb: Experiment and theory

Abstract

The paper presents experimentally obtained permanent electric dipole moment values (μ) in electronically excited B 1Π and D 1Π states of Na8523Rb and Na8723Rb isotopomer molecules for a number of vibrational and rotational levels (v′,J′). The method is based on measuring relative intensities of “forbidden” fluorescence lines appearing due to dc Stark effect induced e/f parity mixing for a particular (v′,J′)-level, combined with electric radio frequency–optical double resonance measurement of Λ-splitting energy Δe,f. The measured D 1Π state μ values are close to 6 D, representing minor changes with the vibrational level v′ varying from 0 to 12 and J′ in the region between 7 and 50, while the measured B 1Π state μ values are about 3 D for v′=4, 5 and 6. The X 1Σ+, B 1Π, and D 1Π dipole moment functions μ(R) are calculated ab initio using the many body multipartitioning perturbation theory for explicit treatment of core-valence correlations. The theoretical and experimental dipole moment estimates are in a perfect agreement for the ground state and the D 1Π state, differing by 15%–25% for the B 1Π state.