Electron capture in collisions of ${\mathrm{Si}}^{3+}$ ions with atomic hydrogen from low to intermediate energies

The electron capture process for the ${\mathrm{Si}}^{3+}$(3$s)$ + H(1$s)$ collisions is investigated by the quantum-mechanical molecular orbital close-coupling (MOCC) method and by the two-center atomic orbital close-coupling (AOCC) method in the energy range of 10${}^{-5}$–10 keV/u and 0.8–200 keV/u, respectively. Total and state-selective cross sections are presented and compared with the available theoretical and experimental results. The present MOCC and AOCC results agree well with the experimental measurements, but show some discrepancy with the calculations of Wang et al. [Phys. Rev. A 74, 052709 (2006)] at $E$ > 40 eV/u because of the inclusion of rotational couplings, which play important roles in the electron capture process. At lower energies, the present results are about three to five times smaller than those of Wang et al. due to the difference in the molecular data at large internuclear distances. The energy behaviors of the electron capture cross sections are discussed on the basis of identified reaction mechanisms.

Figure 1

Adiabatic potential curves for ${\mathrm{SiH}}^{3+}$. The solid lines, dotted lines, and dashed lines represent the Σ, Π, and Δ states, respectively. (a) Singlet states; (b) triplet states.

Figure 2

Radial coupling matrix elements for ${\mathrm{SiH}}^{3+}$. (a) Singlet states; (b) triplet states.

Figure 3

Rotational coupling matrix elements for ${\mathrm{BeH}}^{3+}$. (a) Singlet states; (b) triplet states.

Figure 4

Total electron capture cross sections for the ${\mathrm{Si}}^{3+}$ + H collisions. Present 28-channel MOCC calculation: filled circles; present six-channel MOCC calculation: filled angles; present AOCC calculation: solid line; MOCC results of Wang et al. [7]: dashed line; CTMC results of Wang et al. [7]: dotted line; END results of Guevara et al. [10]: dash-dot-dotted line; LZ results of Herrero et al. [6]: dash-dotted line; the experimental measurement of Bruhns et al. [9]: open circles; the experimental results of Kim et al. [8]: open squares.

Figure 5

State-selective cross sections for electron capture to 3$p^2$, 3$s$3$p$ states (a) and 3$s^2$, 3$s$3$d$ states (b) of the ${\mathrm{Si}}^{2+}$ ions for ${\mathrm{Si}}^{3+}$ + H collision. The present MOCC and AOCC results are compared with the MOCC and CTMC results of Wang et al. [7].

Figure 6

State-selective cross sections for electron capture to 3$s$4$l$ states of ${\mathrm{Si}}^{2+}$ ions for ${\mathrm{Si}}^{3+}$ + H collision. The present MOCC and AOCC results are compared with the CTMC results of Wang et al. [7].

Figure 7

State-selective electron capture cross sections of singlet (a) and triplet (b) states for ${\mathrm{Si}}^{3+}$ + H collision.