Absolute differential scattering cross-sections of electrons from neon, nitrogen and methyl chloride

The relative flow technique is used to obtain absolute DCS in a crossed-beam experiment. A novel gas handling system was designed to facilitate these measurements. The absolute DCS of electrons scattered from neon have been measured from 7 eV down to 0.25 eV. At energies of 2 eV and lower, our results are in excellent agreement with MERT and recent ab initio calculation. At energies higher than 2 eV, our results are in excellent agreement with those of Williams. Thus we propose that neon can be used as a benchmark to test the overall performance of the electron spectrometer at low energies. The angular dependence of absolute vibrationally-elastic DCS of electrons scattered from N$\sb2$ have been measured at 0.55 eV, 1.50 eV, and $\sim$2.22 eV, the second elastic peak of the $\sp2\Pi\sb{\rm g}$ resonance. Our results at these two lower energies are much larger than the previous experimental results, but in close agreement with theoretical calculations by Morrison. By extrapolating our curves to 0$\sp\circ$ and 180$\sp\circ$ using Morrison\u27s curves as a guide, integration gave the total vibrationally-elastic cross sections at these two energies. Our results are within 2-4% of the experimentally measured total cross sections. Methyl Chloride is the simplest saturated hydrocarbon with a single chlorine atom substitution. Two resonances have been assigned in CH$\sb3$Cl, the $a\sb1$(C-Cl,$\sigma\sp*)$ resonance at 3.45 eV and the e(C-H,$\sigma\sp*$) resonance at 5.5 eV. In the elastic channel, the measurements show that dipole scattering dominates at low energies and in the forward direction. In inelastic channels, the C-Cl stretch mode $\nu\sb3(a\sb1)$ is strongly excited by the $\sigma\sp*$(C-Cl) shape resonance, and the C-H stretch mode $\nu\sb4(e)$ is the strongest one excited by the e resonance. The angular dependences for excitation of these two modes are relatively flat. The shapes cannot be explained solely by a few leading terms in the angular momentum expansion arising from the resonance. This suggests that non-resonant scattering may contribute to the angular distribution of these two modes