Theoretical electronic structure of the NaBe molecule

A theoretical study of the low-lying electronic states of NaBe molecule has been investigated via the CASSCF/MRCI (single and double excitations with Davidson correcrtion) method using the correlation-consistent basis set pwCV5Z. Two sets of frozen core orbitals (FCOs) are adopted to estimate the correlation effect of the inner-shell electrons on the molecular properties. The spectroscopic constants are determined for the electronic bound states. The Einstein coefficients, the spontaneous radiative lifetime and the emission oscillator strength have been calculated for the lowest electronic transitions. The ro-vibrational parameters have been obtained for different electronic states by using the canonical functions approach. Twenty-two electronic states are studied theoretically here for the first time. Our evaluation of the potential energy curves leads to significantly off-diagonal Franck-Condon factors for the transitions X²Σ⁺–(2)²Σ⁺ and X²Σ⁺–(1)²Π which shows that the highly diagonal FCFs criterion for laser cooling is not verified for the NaBe molecule.