Detection of Vibrationally ExcitedN2by Superelastic Electron Impact

We have observed electrons scattered superelastically from nitrogen molecules vibrationally excited by quenching collisions with optically excited rubidium atoms. Analysis of the energy gained by the electrons shows that in more than 10% of the quenching collisions the highest energetically allowed vibrational state of ${\mathrm{N}}_2$, $v=5\mathrm{}$, is populated. The relative superelastic cross section for collisions between molecules in this state and electrons is measured and compared with that predicted by detailed balance.