Electron impact cross sections for v=0 to 1 vibrational excitation in CO at electron energies of 3 to 100 eV

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Abstract
Normalised, absolute differential cross sections have been measured for electron-impact excitation of the v=0 to 1 pure vibrational transition in CO. Integral and momentum-transfer cross sections have been obtained from these differential results. Incident electron energies were in the range 3 to 100 eV, and the range of scattering angles 10 to 135 degrees . Comparison of the results is made with pure v=0 to 1 cross sections in N2, as well as with a recent two-potential theory for electron scattering from diatomic molecules. The present CO cross sections are remarkably similar to those in N2, indicating that the long-range effect of the small CO dipole moment is negligible in promoting vibrational excitation. Moreover, a significant peak in the integral and momentum-transfer cross sections is observed at 20 eV. This results from a broad, resonant excitation process in the v=1 channel, and confirms earlier measurements taken at only two scattering angles. Comparison is made of the low-energy integral cross sections with a recent set of swarm data for vibrational excitation.