Excitation of Molecular Nitrogen by Electron Impact

Abstract

Relative cross sections for excitation of the triplet series of molecular nitrogen have been obtained. The cross sections have a maximum within a few volts of threshold as expected for electron exchange collisions. In particular, the C ³II_u state has a sharp maximum within a few tenths of a volt of threshold and then decays sharply. The A ³Σ_u⁺ state has an increasing slope through the Franck—Condon region and then is a strictly linear function of energy for about 1½ V. It subsequently reaches a maximum and starts to decay. This leads to the postulate that the region of increasing slope is caused by the continual excitation of new vibrational levels and that the excitation function of a given vibrational level may be linear to near threshold. This interpretation is shown to be consistent with the experimental data.