5-PI-U-5-SIGMA-G+ TRANSITION IN N-2

Accurate electronic energy curves and wavefunctions of the l5Πᵤ and 15Σg+ states of N2 have been calculated using the multi-configuration self-consistent-field (MC-SCF) method. The5Πᵤ state was predicted by Mulliken who suggested it was important in N2afterglow emissions. The calculated Re and De of the5Πᵤ state are in reasonable accord with estimates of Carroll and Mulliken based on predissociation behaviour of the C3Πᵤ state. The vertical transition energy,5Πᵤ-5Σg+, is calculated to be about 1-8-1-9 eV. The calculated transition probability is zero asymptotically but increases rapidly to shorter distances as the atoms overlap. At R = 1-6 Å the transition probability is about 2 x 105 s-1 or a lifetime of 5 μs for the ground vibrational level. The large and rapidly varying transition probability is a consequence of the difference in s-p mixing in the molecular orbitals of the two states. The dominant contributions to the transition probability arise from the non-orthogonality of the MC-SCF molecular orbitals of the two states. © 1979 Taylor & Francis Group, LLC.