Nascent rotational distributions of N+2(X 2Σ+/sub g/) produced by electron-impact ionization of N2 in a supersonic beam

Laser-induced fluorescence from nascent N+2(X 2Σ+/sub g/) ions produced by electron impact on a N2 supersonic beam was observed. An analysis of the B 2Σ+/sub u/-X 2Σ+/sub g/ (0,0) band shows that the rotational state distributions cannot be represented by a single Boltzmann function, higher N'' levels being overpopulated. Experimental and analytical efforts were made to minimize the influence of cascading and relaxation on the rotational distributions. The rotational energy of N+2(X) thus estimated increases with decreasing electron energy from 2.26 +- 0.16 meV at 300 eV to 4.24 +- 0.27 meV at 25 eV. This trend is explained qualitatively in terms of angular momentum transfer through multipole electron--molecule interactions