Threshold peaks and structures in vibrational excitation of CH3I by electron impact

M Allan, I I Fabrikant
2002 Journal of Physics B: Atomic, Molecular and Optical Physics  
Electron energy loss spectra in CH 3 I reveal the excitation of the nν 3 and ν 1 +nν 3 progressions near threshold, where ν 3 is the C-I stretch and ν 1 the symmetric CH 3 stretch. Relative elastic and vibrationally inelastic cross sections have been measured as a function of electron energy at 135 • . They exhibit many sharp structures at the nν 3 , 1ν 1 and 2ν 1 thresholds. A threshold peak is observed for the excitation of the fundamental 1ν 3 , but only weak threshold peaks are observed for
more » ... ks are observed for the higher overtones. The shapes of the cross sections including the sharp structures are well reproduced by a quasiclassical R-matrix resonance theory with non-local potentials. Thermal population of the 1ν 3 level permitted the measurement of the superelastic cross section.
doi:10.1088/0953-4075/35/4/324 fatcat:oubhpufojjeejkopgaykeps5su