$\mathit{Ab}\hspace{0.5em}\mathit{initio}$ study of charge-transfer dynamics in collisions of C${}^{2+}$ ions with hydrogen chloride

Ab initio quantum chemistry molecular calculations followed by a semiclassical dynamical treatment in the keV collision energy range have been developed for the study of the charge-transfer process in collisions of ${\mathrm{C}}^{2+}$ ions with hydrogen chloride. The mechanism has been investigated in detail in connection with avoided crossings between states involved in the reaction. A simple mechanism driven by a strong nonadiabatic coupling matrix element has been pointed out for this process. A comparative analysis with the halogen fluoride target corresponding to a similar electronic configuration shows a quite different charge-transfer mechanism leading to a very different behavior of the cross sections. Such behavior may be correlated to specific nonadiabatic interactions observed in these collision systems.

Figure 1

Internal coordinates for the ${\mathrm{C}}^{2+}$$-$ HCl collision system.

Figure 2

: Potential-energy curves for the ${}^1$Σ${}^{+}$ (full line) and ${}^1$Π (broken line) states of the ${\mathrm{C}}^{2+}$$-$HCl molecular system at equilibrium, θ $=$ 0°. 1: ${\mathrm{C}}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HCl${}^{+}$(${}^2$Π); 2: ${\mathrm{C}}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HCl${}^{+}$(${}^2$Σ${}^{+}$); 3: ${\mathrm{C}}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}D$ $+$ HCl${}^{+}$(${}^2$Π); 4: ${\mathrm{C}}^{2+}$(1$s^2$2$s^2$)${}^{1}S$ $+$ HCl(${}^1$Σ${}^{+}$) entry channel.

Figure 3

Radial coupling matrix elements between ${}^1$Σ${}^{+}$ states of the ${\mathrm{C}}^{2+}$$-$ HCl molecular system at equilibrium, θ $=$ 0°. Same labels as in Fig. 2.

Figure 4

Rotational coupling matrix elements between ${}^1$Σ${}^{+}$ and ${}^1$Π states for the ${\mathrm{C}}^{2+}$$-$ HCl molecular system at equilibrium, θ $=$ 0°. Same labels as in Fig. 2. $\mathrm{rot}11=\langle 1^1\Pi \left|i\mathrm{Ly}\right|1^1{\Sigma }^{+}\rangle$; $\mathrm{rot}22=\langle 2^1\Pi \left|i\mathrm{Ly}\right|2^1{\Sigma }^{+}\rangle$; $\mathrm{rot}32=\langle 3^1\Pi \left|i\mathrm{Ly}\right|2^1{\Sigma }^{+}\rangle$; $\mathrm{rot}34=\langle 3^1\Pi \left|i\mathrm{Ly}\right|4^1{\Sigma }^{+}\rangle$.

Figure 5

Total and partial charge-transfer cross sections for the ${\mathrm{C}}^{2+}$$-$ HF collision system at equilibrium, θ $=$ 0°. Full line: with translation factors; broken line: without translation factors. sectot: total cross section; sec32: partial cross section on ${}^1$Σ${}^{+}${C${}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HF${}^{+}$(${}^2$Σ${}^{+}$)}; secpi32: partial cross section on ${}^1$Π{C${}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HF${}^{+}$(${}^2$Σ${}^{+}$)}; sec31, partial cross section on ${}^1$Σ${}^{+}${C${}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HF${}^{+}$(${}^2$Π)}; secpi31: partial cross section on ${}^1$Π{C${}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HF${}^{+}$(${}^2$Π)}.

Figure 6

Total and partial charge-transfer cross sections for the ${\mathrm{C}}^{2+}$$-$ HCl collision system at equilibrium, θ $=$ 0°. Full line: transition to ${}^1$Σ${}^{+}$ states; broken line: transition to ${}^1$Π states. sectot: total cross section; sec43: partial cross section on {C${}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}D$ $+$ HCl${}^{+}$(${}^2$Π)}; sec42: partial cross section on {C${}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HCl${}^{+}$(${}^2$Σ${}^{+}$)}; sec41: partial cross section on ${}^1$Σ${}^{+}${C${}^{+}$(1$s^2$2$s^2$2$p$)${}^{2}P$° $+$ HCl${}^{+}$(${}^2$Π)}.