Excitation of High Vibrational States ofN2and CO via Shape Resonances

The vibrational cross section to $v=8,9\mathrm{}$, and 10 by electron impact on ${\mathrm{N}}_2$ and CO has been measured in the energy range 2-4 eV. In this energy range vibrational excitation proceeds predominantly via a compound state, and decay into high vibrational states can occur. At the first peak the ratio of cross sections for $v=8:9:10\mathrm{}$ is 1: 0.31: 0.11 in ${\mathrm{N}}_2$, and 1: 0.51: 0.25 in CO. These ratios are largely determined by the quantum-mechanical penetration through the centrifugal barrier.