THE B[-X ELECTRONIC-SPECTRUM OF N-2 -HE

Abstract

The electronic spectrum of N2+–He has been measured in the region corresponding to the N2+ B 2Σ+u←X 2Σ+g origin transition. The spectrum was recorded by photoexciting a mass selected beam of N2+–He ions and detecting N2+ fragments. A likely process for the fragmentation involves fluorescence to a vibrationally excited level of the ground electronic state followed by vibrational predissociation. The observed spectrum exhibits well resolved discrete structure and bears a remarkable resemblance to a cold N2+ spectrum suggesting that the potential between the N2+ ion and helium atom in both the X and B electronic states, has at most only a small barrier to internal rotation. Measurement of the s..