Radiative Lifetime of the "Forbidden"a¹Πg←X¹Σg⁺Transition of N₂

Using the second order polarization propagator method we have calculated the band oscillator strengths of the "forbidden" Lyman-Birge-Hopfield band system, a 1 Π g ← X 1 Σ g + , of N 2 and the radiative lifetime τ( v' ) of the a 1 Π g state for 0 ⩽ v' ⩽ 4. We find that τ(0) = 58.6 μsec and τ(4) = 68.2 μs. About 95 per cent of the intensity are magnetic dipole contributions and only about 5 per cent come from the electric quadrupole radiation.