Use of relativistic effective core potentials in calculating the electronic spectrum of the antimony dimer
A relativistic configuration interaction study including the spin-orbit coupling has been carried out for a large number of electronic states for the antimony dimer and comparisons with analogous results for the isovalent Bi2 molecule have been made. Bond lengths re, vibrational frequencies ωe, excitation energies Te, and dissociation energies De have been computed for all bound states up to 40 000 cm-1, as well as transition probabilities and radiative lifetimes based on electric-dipole matrix elements. The calculations confirm that the A1u state derives mainly from the π→π* 3∆u λ-s state and not from the lower-lying 3Σ+u. The lifetime of this state (0.3 ms) is computed to be 50 times shorter than for the B0+u state, suggesting that emissions from either of these states will be quite difficult to observe in gas-phase studies. By contrast the lifetime of the D0+u state is relatively short (35.6 ns), consistent with the fact that the D-X band system is quite intense. No suitable candidate is indicated for the K-X transition observed by Sontag and Weber, however, and thus it is suggested that the corresponding spectrum is a part of the D-X system.