Elastic and vibrationally inelastic scattering of low-energy electrons frompropane

Abstract

In a crossed-beam experiment, differential cross sections (DCS) forelastic and vibrationally inelastic scattering of electrons from propanehave been measured in the energy range E = 0.5–10 eV.Absolute values are obtained by using e−–Hescattering as a reference system. For elastic scattering, the measured DCS areanalysed by phase-shift analysis and modified effective-range theory andthen extrapolated into the experimentally inaccessible regions. In thisway, the complete set of elastic DCS for E = 0–10 eVand θ = 0°–180° isobtained. Integral and momentum transfer cross sections are determined,which are compared with the results of electron transmission and swarmexperiments. For vibrationally inelastic scattering, the observed vibrationalexcitation (VE) processes are divided into three groups: (i) CHxstretching modes, with a mean energy loss of ΔE = 366 meV; (ii) CHxdeformation modes, with ΔE = 175 meV;(iii) CC carbon chain vibrations, with ΔE = 122 meV.Absolute differential and integral cross sections are determined for each of thethree mode groups. Two principal VE mechanisms are responsible forthe observed processes: direct VE for energies below 3 eV and resonantVE for energies around 7–8 eV. The Born dipole approximation is usedto analyse the data in the region of direct VE at low energies.