RELATIVISTIC CONFIGURATION-INTERACTION STUDY OF THE LOW-LYING ELECTRONIC STATES OF BI-2

Relativistic effective core potentials have been employed in the framework of a spin-orbit configuration interaction treatment to compute potential curves, spectroscopic constants, and transition probabilities between pairs of vibrational states of the Bi2 molecule. The calculations find a steady increase in bond length for the lowest four states as a result of successive π→π* excitations en route from the X0 g+ ground state to the doubly excited 5Σ g+0g+, in good agreement with measured data. The corresponding 1g state with a Te value near 12 000 cm-1 has not yet been located experimentally. The next most stable λ-s, state is found to be 3Δu, with Ω components increasing in energy in the order, 2u< 3u<1u, of which only the latter has electric dipole-allowed transitions to X0g+. It is argued that the 1u species should be identified with the observed b state instead of the 3u component, especially since its calculated energy splitting relative to a2u is in much better agreement with the observed b-a separation than is the 3u-2u value. The radiative lifetime of the A0u+ state is calculated to be 72 μs, whose result indicates that a previous experimental determination of this quantity in the presence of argon vapor needs to be reevaluated. In general it appears that the present computed Te values are accurate to within 500-1500 cm-1 of corresponding observed results, and that bond lengths are overestimated by 0.1 Å because of both deficiencies in the RECP employed as well as the failure to include the bismuth 5d electrons in the CI active space. © 1995 American Institute of Physics.