Charge transfer in slow collisions of ${\mathrm{C}}^{6+}$ with H below $1\mathrm{keV}∕\mathrm{amu}$

We reexamine the charge transfer cross sections for ${\mathrm{C}}^{6+}+\mathrm{H}$ collisions for energies below $1\mathrm{keV}∕\mathrm{amu}$ using a fully quantum mechanical approach, based on the hyperspherical close-coupling method. Whereas most previous theoretical and experimental data agree well for the dominant charge transfer to the ${\mathrm{C}}^{5+}(n=4)$ states, there is significant disagreement among the theories for the transition to the weaker $n=5$ states. Using the present quantum mechanical calculations we analyze the origin of the discrepancy among these previous calculations. We further extend the calculations to collision energies down to about 1 eV and show that electron capture to the $n=5$ states begins to dominate over the $n=4$ states.

Figure 1

(Color online) Hyperspherical potential curves for ${\mathrm{CH}}^{6+}$. This figure shows only the $I=0$ channels. The insets show areas with complicated avoided crossings in more detail.

Figure 2

(Color online) Present results for the charge transfer cross sections for the processes ${\mathrm{C}}^{6+}+\mathrm{H}\left(1s\right)\to {\mathrm{C}}^{5+}(n=4,5)+{\mathrm{H}}^{+}$.

Figure 3

(Color online) “Electronic” part of the hyperspherical potential curves for ${\mathrm{CH}}^{6+}$. Note that the curves have been diabatized. See text for more details.

Figure 4

(Color online) Comparison of calculated total charge transfer cross sections for ${\mathrm{C}}^{6+}+\mathrm{H}\left(1s\right)\to {\mathrm{C}}^{5+}(n=4,5)+{\mathrm{H}}^{+}$. Present results are shown in solid lines. Other theoretical predictions are shown in symbols. Both the results of Caillat et al. [6] and those of Kimura and Lin [7] are obtained from AO calculations with straight-line trajectories. Results of Harel et al. [4] are calculated using MO basis and straight-line trajectories. Results of Green et al. [3] are obtained from MO calculations using curved trajectories. The dotted line connecting the results of Caillat et al. indicates an energy dependence different from others.

Figure 5

(Color online) Comparison of the quantal HSCC and semiclassical straight-line trajectory AO results for the impact parameter weighted probability as a function of impact parameter at $E=0.5\mathrm{keV}∕\mathrm{amu}$.

Figure 6

(Color online) Same as Fig. 5, but for $E=50\mathrm{eV}∕\mathrm{amu}$. Note that the AO results for the transition to ${\mathrm{C}}^{5+}(n=5)$ have been scaled down by a factor of $1∕3$.

Figure 7

(Color online) Impact parameter weighted probability as a function of impact parameter at $E=1\mathrm{eV}$.