Molecular-Beam Measurements of the Emission Spectrum and Radiative Lifetime of N2 in the Metastable E 3Σg+ State

Electron-impact excitation of a molecular beam of nitrogen was used to produce the metastable E 3Σg+ state. This state, which lies 11.87 eV above the ground state, has recently been observed in a number of electron-impact experiments. This paper reports the emission spectrum from the molecular beam, and identifies three forbidden electronic transitions, E 3Σg+ → A 3Σu+, E 3Σg+ → B 3Πg, and E 3Σg+ → C 3Πu. Approximate absolute transition probabilities are determined. The radiative lifetime of the E state is 270 ± 100 μsec, and the equilibrium internuclear distance is 1.16 ± 0.02 Å.