Electron-impact ionization and dissociation of C₂D⁺

Abstract

Absolute cross sections for electron-impact single ionization, dissociative excitation and dissociative ionization of the ethynyl radical ion (C₂D$^+)$ have been measured for electron energies ranging from the corresponding reaction thresholds to 2.5 keV. The animated crossed electron-ion beam experiment is used and results have been obtained for the production of C₂D²⁺, C²⁺, C$_2^+$, CD⁺, C⁺ and D⁺. The maximum of the cross section for single ionization is found to be (2.01 ± 0.02) × 10^-17 cm², at the incident electron energy of 105 eV. Absolute total cross sections for the various singly charged fragments production are observed to decrease by a factor of almost three, from the largest cross-section measured for C⁺, over C$_2^+$ and CD⁺ down to that of D⁺. The maxima of the cross sections are obtained to be (14.5 ± 0.5) × 10^-17 cm² for C$_2^+$, (12.1 ± 0.1) × 10^-17 cm² for CD⁺, (27.7 ± 0.2) × 10^-17 cm² for C⁺ and (11.1 ± 0.8) × 10^-17 cm² for D⁺. The smallest cross section is measured to be (1.50 ± 0.04) × 10^-18 cm² for the production of the doubly charged ion C²⁺. Individual contributions for dissociative excitation and dissociative ionization are determined for each singly-charged product. The cross sections are presented in closed analytic forms convenient for implementation in plasma simulation codes. Kinetic energy release distributions of dissociation fragments are seen to extend from 0 to 6 eV for the heaviest fragment C$_2^+$, up to 11.0 eV for CD⁺, 14.2 eV for C⁺ and 11.2 eV for D⁺ products.