The5Πu-5Σg+transition in N2

Accurate electronic energy curves and wavefunctions of the 15Π u and 15σ g + states of N2 have been calculated using the multi-configuration self-consistent-field (MC-SCF) method. The 5Π u state was predicted by Mulliken who suggested it was important in N2 afterglow emissions. The calculated R e and D e of the 5Π u state are in reasonable accord with estimates of Carroll and Mulliken based on predissociation behaviour of the C 3Π u state. The vertical transition energy, 5Δ u -5Π g +, 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 × 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.