Rotational Excitation by Slow Electrons

Abstract

Cross sections are calculated for rotational excitation of a homonuclear diatomic molecule by collisions with very slow electrons. The mechanism is assumed to be the long-range quadrupole interaction. The Born approximation is shown to be correct in the low-energy limit. The results are applied to calculation of energy losses in ${\mathrm{N}}_2$, and comparison is made with values inferred from swarm and cross-modulation experiments. At energies below 0.29 ev, the threshold for vibrational excitation, losses are ∼ twice the experimental values, but many times larger than the value ($\frac{2m}{M}$) for elastic losses only.