Quadrupole-Allowed Transitions in the Electron-Impact Spectrum of N2

Abstract

The forbidden transitions observed in the nitrogen spectrum below 12.5 V have been studied by electron‐impact methods. Since the theory indicates that electric quadrupole transitions are preferred to singlet—triplet in electron‐impact spectra at intermediate energies, the observed transitions are probably electric quadrupole allowed. This has been demonstrated for the 12.25‐V transition by studying its relative intensity as a function of the scattering angle. The data on the 11.86‐V transition are also compatible with an electric quadrupole transition. In addition, new data on the Lyman—Birge—Hopfield bands in the 60–400‐V energy range indicate that the intensity distribution among vibrational levels is independent of energy.