Excitation of the four fundamental vibrations of CH4 by electron impact near threshold

Absolute differential elastic and vibrational excitation cross sections have been measured for CH4 at 90 degrees and from 0.1 to 1.5 eV with the resolution of all four vibrational modes. Threshold peaks were observed in the excitation of the nu(1), nu(3) and nu(4) modes, but not in the nu(2) mode. These results are in good agreement with the recent calculation of Nishimura and Gianturco. No near-threshold structures were observed.