Accurate a b i n i t i o calculations of radiative transition probabilities between the A 3Σ+u, B 3Πg, W 3Δu, B′ 3Σ−u, and C 3Πu states of N2

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Abstract
Potential energy and electronic transition moment functions for the lowest five triplet states of N2 have been calculated from highly correlated multiconfiguration-reference CI wave functions. From the calculated transition moments and RKR potential energy functions, radiative transition probabilities and lifetimes have been evaluated which are believed to be accurate within 15%. The theoretical lifetime of 36.7 ns of the C 3Πu state is in close agreement with the most recent experimental values. The calculated lifetimes of the B 3Πg state decrease from 13.4 μs for v′=0 to 4.82 μs for v′=12. The values for v′=5 to v′=12 are in good agreement with recent LIF measurements. The lifetimes for v′=0 to v′=4, however, are considerably larger than most previously measured values. The fact that the calculated values are very stable with respect to improvements of the electronic wave functions leads us to conclude that the experimental values are too low. Empirical transition moment functions for the B–A system are apparently too steep, and the moments at short distances much too large. Previous estimates of the lifetimes of the W 3Δu vibrational levels are three times smaller than our calculated values, whereas estimates for the B 3Σ−u state agree reasonably well with the theoretical results.

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