Elastic and inelastic processes in ${\mathrm{H}}^{+}+{\mathrm{C}}_2{\mathrm{H}}_6$ collisions below the $10\text{−}\mathrm{keV}$ regime

Charge-transfer processes in collisions of ${\mathrm{H}}^{+}$ ions with ${\mathrm{C}}_2{\mathrm{H}}_6$ molecules are investigated theoretically below $10\text{−}\mathrm{keV}$ collision energies within a molecular representation. Converged total as well as differential cross sections are obtained in this energy range within a discrete basis of electronic states computed by ab inito methods. The present collision system suggests that the combination of the Demkov-type and Landau-Zener–type mechanisms primarily governs the scattering dynamics for the flux exit from the initial channel. The present charge-transfer cross sections determined are found to agree very well with all available experimental data below a few keV, but begin to deviate above $3\mathrm{keV}$, in which the present results slowly decrease, while measurements stay nearly constant. From the study of the electronic state calculation, we provide some information on fragmented species, which should help shed some light on the fragmentation mechanism and process of ${\mathrm{C}}_2{\mathrm{H}}_6^{+}$ ions produced after charge transfer. In addition, the vibrational effect of the initial target to charge transfer is examined.

Figure 1

Schematic diagram indicating the molecular axis orientation employed for the ${[\mathrm{H}+{\mathrm{C}}_2{\mathrm{H}}_6]}^{+}$ collision system.

Figure 2

The adiabatic potentials of the ${[\mathrm{H}+{\mathrm{C}}_2{\mathrm{H}}_6]}^{+}$ system for the (a) (i), (b) (ii), and (c) (iii) directions (see text for definition) of approach of the proton.

Figure 3

Representative radial couplings between the initial and electron-capture states for all three configurations.

Figure 4

Differential cross sections for the (a) (i), (b) (ii), and (c) (iii) configurations at $0.5\mathrm{keV}$ (left panel) and $1.5\mathrm{keV}$ (right panel) from the initial state 3 to the electron captured state 4. Solid line, direct elastic scattering; dashed line, electron capture.

Figure 5

Differential cross sections for small scattering angles up to 10° at $0.5\mathrm{keV}$ from the initial state 3 to the electron capture state 4 are shown. Solid line, direct elastic scattering; dashed line, electron capture.

Figure 6

Differential cross sections averaged over three configurations.

Figure 7

$S$-matrix elements for three configurations.

Figure 8

Partial cross sections from each channel for the (i), (ii), and (iii) molecular configurations.

Figure 9

(a) The averaged partial cross sections for the 1, 2, and 4 state populations. (b) Partial cross sections from 3 state to 4 state for (i), (ii), and (iii) configuration.

Figure 10

(a) Total electron-capture cross sections of the ${\mathrm{H}}^{+}+{\mathrm{C}}_2{\mathrm{H}}_6$ collisions averaged over (i), (ii), and (iii) configurations. (b) [Electron $\text{capture}+\text{excitation}$] cross sections of the process (1b).

Figure 11

Total electron capture cross sections of the ${\mathrm{H}}^{+}+{\mathrm{C}}_2{\mathrm{H}}_6$ system along with the estimates by Janev et al. and the observed data by Kusakabe et al.

Figure 12

Total cross sections as a function of the number of atoms in the molecule at specific energies as shown.