Absolute cross sections and kinetic energy release distributions for electron impact ionization and dissociation of CD+

Abstract

Absolute cross sections for electron impact dissociative excitation and ionization of CD+ leading to the formation of ionic products (D+, C+, C2+ and C3+) are reported in the energy range from their respective thresholds to 2.5 keV. Around the maximum, cross sections are found to be (10.5 ± 1.0) × 10−17 cm2, (20.6 ± 3.5) × 10−17 cm2, (1.20 ± 0.11) × 10−17 cm2 and (8.2 ± 1.5) × 10−20 cm2 for D+, C+, C2+ and C3+, respectively. In the very low-energy region, dissociative excitation leading to the C+ formation dominates over the D+ one. The cross section for dissociative ionization (C+ + D+ formation) is found to be (6.9 ± 1.3) × 10−17 cm2 around 105 eV and the corresponding threshold energy is (22.1 ± 0.5) eV. The animated crossed-beams method is used and the analysis of ionic product velocity distributions allows the determination of the kinetic energy release distributions. They are seen to extend from 0 to 15 eV both for C+ and for D+, and up to 40 eV both for C2+ and for C3+. For singly charged products, the comparison of the present energy thresholds and kinetic energy release with published data allows the identification of states contributing to the observed processes. In particular, contributions from primary ions formed in the a3Π metastable state are perceptible. At fixed electron energy, the cross sections for the various ionization channels are seen to reduce exponentially with the potential energy of each dissociated ion pair. Anisotropies are estimated to be in the range 8 ± 2% for both C+ and D+. The total CD+ single ionization cross section calculated by application of the Deutsch–Märk formalism is found to be in good agreement with experimental results.