On the radiative lifetimes of the a 3Σ+ state of NO+

The radiative lifetimes of the lowest excited triplet state of NO+ have been evaluated using new integral and CI programs for the spinless and the spin dependent components of the molecular Hamiltonian. The Rayleigh–Schrödinger perturbation theory, compared to direct CI techniques, provides a numerically more stable and rapidly convergent expansion for the spin–orbit terms of the molecular wave functions. Based on this theory, we have performed the analysis of the Rayleigh–Schrödinger components of the singlet–triplet transition moment and found that the most important contribution to the radiative lifetimes is given by the second excited B 1Π state and not by the lowest A 1Π state as previously assumed on energy grounds. The radiative lifetimes computed for the lowest five vibrational states of a 3Σ+, resulting from the difference of two large contributions from the B 1Π and the A 1Π states, are found extremely sensitive to small variations in the computed 〈1Σ+‖μ‖B 1Πβ〉 transition dipole function and to the 〈a 3Σ+,1,1‖HLαSα‖A 1Πβ,0, 0〉 spin–orbit interaction. Using matrix elements evaluated at two levels of CI, the radiative lifetimes are estimated 330∼270 and 270∼250 ms, respectively.