Relativistic configuration interaction calculations of the low-lying states of TlF

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Abstract
Relativistic configuration interaction calculations (including spin-orbit interaction) are carried out for the nine low-lying ω–ω states arising from the 1Σ+, 3Π, 1Π, 3Σ−, 3Σ+, and 3Δ Λ-S states of TlF. Our calculations confirm the earlier assignment of experimentally observed spectra to some of these states. We have calculated the spectroscopic properties of both experimentally observed states (1Σ+0+, 3Π0+, 3Π1, 1Π1) and 3Π0−, 3Π2, 0−(II), 2(II), and 0+(III) states. The calculated spectroscopic properties are in good agreement with experimental values. The potential energy curves of the excited states of TlF [3Π0+, 3Π1, 3Π2, 3Π0−, 0−(II), 0+(III), and 2(II)] contain maxima thus confirming the recent experimental observations which predict potential barriers in the excited Π states. Vibrational bands higher than ν′=3 for 3Π0+ and ν′=8 for 3Π1 could not be observed. The present calculations explain this based on the crossing of repulsive 0− (I) state with 3Π0+ and 3Π1 thus leading to predissociation.