Strong mode dependence of the 3.8-eV resonance in CO2 vibrational excitation by electron impact - art. no. 060701

We have made a systematic observation for integrated cross sections that vi brational excitation modes are found to show quite different energy depende nce in the 3.8-eV shape resonance peak in a CO, molecule. This feature aris es from the different interaction scheme for excitation to each mode, i.e., the weak polarization interaction for excitation to the symmetric stretchi ng mode, weak dipole interaction to the bending mode, and strong dipole int eraction to the asymmetric stretching mode. The asymmetric stretching shows a sharp increase in differential cross sections (DCSs) toward small-angle scattering due to the strong dipole interaction, which washes out resonance features seen at intermediate angles. DCSs for the symmetric and bending m odes clearly show conspicuous features at a wide range of the scattering an gle around 3.8-eV shape resonance.