Abstract

Ab initio multireference configuration interaction calculations including spin–orbit coupling are carried out for valence electronic states of the TeF molecule and compared to the results for the isovalent IO system obtained earlier at a similar level of theoretical treatment [S. Roszak et al., J. Phys. Chem. A 104, 2999 (2000)]. The calculated spectroscopic constants are in good agreement with available experimental data. It is shown that the X 2Π(σ2π4π*3) ground state is much more strongly bound in TeF (calc. De=25 480 cm−1) due to the greater ionic character of bonding in this system as compared to IO. The lowest excited states of TeF are found to be A 4Σ1/2,3/2− and B 2Σ1/2− which result from the π→σ* electronic excitation. In contrast to IO, the Π2(σ2π3π*4) excited state has a repulsive potential curve and is not expected to be a factor in the low-energy spectroscopy of TeF. Particular emphasis is placed on computation of the transition moments and radiative lifetimes of the TeF electronic states. Most transitions are found to be quite weak, with the strongest of them, B 2Σ1/2−→X1 2Π3/2, characterized by a τ value of 9.5 μs. The two C 2Δ spin components, Ω=5/2 and 3/2, not yet observed experimentally, are predicted to lie ∼1800 cm−1 above B 2Σ1/2− and have partial lifetimes for transitions to the X1 and X2 states which are only slightly longer than those calculated for the B→X1,2 transitions.

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