Electron-impact dissociation and ionization of OH+ and OD+ ions

Absolute cross sections for electron impact ionization and dissociation of OH+ and OD+ leading to the formation of the OH2+, O+, O2+, O3+ and D+ ions have been measured by applying the animated electron-ion beam method in the energy range from the respective reaction thresholds up to 2.5 keV. The maximum of the single ionization cross section is found to be (0.95  ±  0.02) × 10-19 cm2 at 155 eV. The maximum total cross sections for O+ and D+ fragments production are observed to be (15.7  ±  0.2) × 10-17 cm2 at 95 eV and (10.8  ±  0.5) × 10-17 cm2 at 95 eV, respectively. The cross sections for O2+ and O3+ are much smaller, (5.37  ±  0.04) × 10-18 cm2 at 135 eV and (7.95  ±   0.23) × 10-20 cm2 at 315 eV, respectively. The collected data are analyzed in details in order to determine separately the contributions of dissociative excitation and of dissociative ionization to the O+ and D+ fragments production

Electron-impact ionization and dissociation of C(2)D(+)

Absolute cross sections for electron-impact single ionization, dissociative excitation and dissociative ionization of the ethynyl radical ion (C(2)D(+)) 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 C(2)D(2+), C(2+), C(2)(+), CD(+), C(+) and D(+). The maximum of the cross section for single ionization is found to be (2.01 +/- 0.02) x 10(-17) cm(2), 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) x 10(-17) cm(2) for C(2)(+) (12.1 +/- 0.1) x 10(-17) cm(2) for CD(+) (27.7 +/- 0.2) x 10(-17) cm(2) for C(+) and (11.1 +/- 3.8) x 10(-17) cm(2) fo D(+). The smallest cross section is measured to be (1.50 +/- 0.04) x 10(-18) cm(2) for the production of the doubly charged ion C(2+). 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

I. Electron-impact ionization and dissociation of C

Absolute cross-sections for electron-impact ionization and dissociation of C2 H2+ and C2 D2+ have been measured for electron energies ranging from the corresponding thresholds up to 2.5 keV. The animated crossed beams experiment has been used. Light as well as heavy fragment ions that are produced from the ionization and the dissociation of the target have been detected for the first time. The maximum of the cross-section for single ionization is found to be (5.56±0.03)×10-17 cm2 around 140 eV. Cross-sections for dissociation of C2 H2+ (C2 D2+) to ionic products are seen to decrease for two orders of magnitude, from C2D+ (12.6±0.3)×10-17 cm2 over CH+ (9.55±0.06)×10-17 cm2, C+ (6.66±0.05)×10-17 cm2, C2+ (5.36± 0.27)×10-17 cm2, H+ (4.73±0.29)× 10-17 cm2 and CH2+ (4.56±0.27)×10-18 cm2 to H2+ (5.68±0.49)×10-19 cm2. Absolute cross-sections and threshold energies have been compared with the scarce data available in the literature

Electron impact single ionization and dissociative excitation of H3O+, HD2O+ and D3O+

First absolute cross sections for electron impact single ionization of H3O+, HD2O+ and D3O+ and for dissociative excitation (DE) producing H+ and D+ are reported. The animated crossed electron-ion beam method has been employed in the energy range from threshold to 2500 eV. The maxima of these cross sections are found to be unusually small (<1 x 10(-17) cm(2)). The ionization threshold energies are determined to be 24.7 +/- 0.5, 24.4 +/- 0.5 and 24.0 +/- 0.5 eV for H3O+, HD2O+ and D3O+, respectively. The observed DE threshold energies lie in the range 10-12.5 eV and the maximum kinetic energies released are between 3 and 4 eV. Significant differences are observed between the results obtained for the three isotopomers

Absolute cross sections for electron impact ionization and dissociation of O-2(+)

Absolute cross sections for electron impact single ionization, dissociative excitation and dissociative ionization of O-2(+) were measured in the energy range from threshold to about 2.5 keV by means of a crossed beam set-up. The analysis of product velocity distributions has been applied in order to (i) separate the three processes and (ii) determine the kinetic energy release distribution of ionic fragments. Dissociation is seen to dominantly follow the ionization and the excitation processes, the maximum of the cross sections being found to be (2.20 +/- 0.09) x 10(-17) cm(2), (5.3 +/- 1.0) x 10(-17) cm(2) and (22.0 +/- 4.6) x 10(-17) cm(2) for simple ionization, dissociative ionization and dissociative excitation, respectively. The total kinetic energy released to the fragments is seen to extend up to about 20 eV

Electron-impact dissociation and ionization ofCN+ions

Absolute cross sections are reported for electron-impact ionization and dissociation of CN+ ions. Simple ionization to CN2+ ions and formation of singly charged C+ and N+ and doubly charged C2+ and N2+ fragments have been investigated. The animated electron-ion crossed-beam method has been applied in the energy range from the respective reaction threshold sup to2.5keV.The maximum of the simple ionization cross section is found to be (5.37±0.14)×10−18 cm2 at115eV.The maximum total cross sections for N+ and C+ fragment production are found to be (22.2±2.7)×10−17 and(18.9±1.2)×10−17 cm2 at85eV,respectively.Byperformingcareful magnetic field scans of the collected ions, contributions of dissociative excitation and dissociative ionization to the C+ and N+ fragment production are determined separately. The cross sections for asymmetric dissociative ionization to C2+ and N2+ are found to be more than one order of magnitude smaller. The kinetic energy release distributions are determined for all dissociation processes at selected electron energies. These distributions, together with the energy thresholds, provide additional information about the ground and excited states of the molecular ion

Electron-impact dissociation and ionization of NO+ions

Absolute cross sections for electron-impact ionization and dissociation of NO+ ions are reported. Simple ionization to NO2+ ion and production of singly charged N+ and O+ and doubly charged N2+ and O2+ fragments have been investigated. The animated electron-ion crossed-beam method is applied in the energy range from the respective thresholds up to 2.5 keV. The maximum of the simple ionization cross section is found to be (3.49 ± 0.07) × 10−17 cm2 at 135 eV. The total cross sections for N+ and O+ fragments at the maximum are found to be (13.9 ± 1.0) × 10−17 cm2 and (14.0 ± 1.4) × 10−17 cm2, respectively, both at an energy of 85 eV. By performing careful magnetic field scans of the detected signal, contributions of dissociative excitation and dissociative ionization to N+ and O+ production are determined separately. The cross sections for asymmetric dissociative ionization to N2+ and O2+ are found to be over one order of magnitude smaller. Distributions of the kinetic energy release to the fragments are determined for all dissociation processes

A crossed-beam experiment for electron impact ionization and dissociation of molecular ions: its application to CO+

A crossed electron-ion beam experimental set-up has been upgraded for the study of electron impact ionization and dissociation of molecular ions by means of ionic product detection. Both the experimental set-up and the data analysis procedures are described in detail for the estimation of ( i) absolute cross sections, ( ii) kinetic energy release distributions ( KERD) and ( iii) anisotropies of angular distributions. Absolute cross sections are obtained separately for dissociative excitation ( DE) and for dissociative ionization ( DI). A double focusing magnetic field analyser is used for the observation of product velocity distributions, in the laboratory frame, at selected electron energies. The KERD in the centre of mass frame is calculated from the measured velocity distribution as well as the anisotropy of the angular distribution with respect to the initial orientation of the molecular ions. Results are reported for dissociative ionization and dissociative excitation of CO+ to C+ and O+ fragments in the energy range from about 5 eV to 2.5 keV. Absolute cross sections for DE at maximum, i. e. for an electron energy around 35 eV, are found to be ( 9.69 +/- 2.08) x 10(-17) cm(2) and ( 6.24 +/- 1.33) x 10(-17) cm(2), for C+ and O+, respectively, and the corresponding threshold energies are found to be ( 8.5 +/- 0.5) eV and ( 14.8 +/- 0.5) eV. The DE process leading to C+ production is seen to dominate at low electron energies. For DI, the absolute cross section is found to be ( 12.56 +/- 2.38) x 10(-17) cm(2) around 125 eV and the corresponding threshold energy is ( 27.7 +/- 0.5) eV. KERDs, which extend from 0 to 24 eV both for C+ and O+, exhibit very different shapes at low electron energy but similar ones above 100 eV, confirming the role observed respectively for DE and DI. The groups of states contributing to the different processes are identified by comparing present energies thresholds values and the KERDs with theoretical values. Anisotropies are estimated to be in the range 3-6% for both C+ and O+