Absolute partial cross sections and kinetic energy analysis for the electron impact ionization of propene

Abstract

We present absolute partial electron impact ionization cross sections for propene in the electron energy range between threshold and 1000 eV measured with a two sector field double focussing mass spectrometer. Ion beam profiles have been measured at all electron energies by applying a deflection field method. In combination with a three-dimensional ion trajectory simulation of ions produced in the ion source ion kinetic energy distribution functions and discrimination factors can be derived form these data. Multiplication of these discrimination factors with the measured ion signals leads to relative partial cross sections. Normalization of the sum of the relative partial cross sections to an absolute total cross section gives absolute partial cross section values. The initial kinetic energy distributions of several fragment ions show the presence of two or more contributions exhibiting different electron energy dependencies. Differential cross sections with respect to initial kinetic energy of the ions are given and related to specific ion production channels. The high energetic parts of the initial kinetic energy distributions are assigned to the Coulomb explosion of doubly charged short-lived intermediates. The reaction C 3H 5 2+ → C 2H 2 + + CH 3 + has been studied quantitatively in the ion source, the first field free region and the second field free region of the two sector field mass spectrometer yielding a measured mean kinetic energy release of 4.99 ± 0.5 eV, 4.85 ± 0.5 eV and 5.5 ± 0.5 eV, respectively in good agreement with a theoretical estimation.