Abstract

The B³Π₀₊ → X¹Σ₀₊ electronic transition in IF appears to be an attractive candidate as a shortwavelength chemical laser system. To evaluate whether a chemical pumping scheme can be devised to populate the B³Π₀₊ state, detailed studies of the low-lying electronic structure of IF have been undertaken. These studies were carried out using an ab initio approach based on a (λ,S) coupling scheme. Spin-orbit effects were evaluated using a one-center perturbative treatment. Our results indicate that the B³Π₀₊ state is predissociated by both the c³Π₀₊ and $Y^3{\text{Σ}}_{0+}^{-}$ states; the lowest predissociation is by c³Π₀₊ at the v' = 9 level of the B state. The lowest reservoir state, A'³Π₂, lies at ~13,600 cm⁻¹, thereby ruling out direct excitation processes for IF with pump molecules such as O₂ [a¹Δ_g], Of particular interest is the lowest ¹Π₁, state for which preliminary calculations indicate a binding energy of ~2800 cm⁻¹. This contrasts with the l₂ system where the lowest ¹Π₁ state is found to be repulsive. Further studies of the low-lying electronic states that can be reached by ${\text{N}}_2{A}^3{\text{Σ}}_u^{+}$ excitation are in progress.

© 1986 Optical Society of America