Observation of significant differences in charge transfer between collisions ofH+ions withH2and withD2molecules in the high-eV to low-keV range

Abstract

Significant difference in charge transfer cross sections between collisions of ${\mathrm{H}}^{+}$ ions with ${\mathrm{H}}_{2}$ and ${\mathrm{D}}_{2}$ molecules has been observed in the energy range from 0.18 to 1.5 keV/u. The cross section ratio $\ensuremath{\sigma}{(}_{{\mathrm{D}}_{2}})/\ensuremath{\sigma}{(}_{{\mathrm{H}}_{2}})$ of charge transfer from ${\mathrm{D}}_{2}$ and ${\mathrm{H}}_{2}$ has been found to be $0.59\ifmmode\pm\else\textpm\fi{}0.08$ at 0.18 keV/u and gradually increases at higher energies and, then, eventually approaches unity at the highest energies around 2 keV/u. Nevertheless, the difference due to the isotope effect is pronounced even at high eV/u to 1 keV/u regions. This marked feature originates from a combination of small offset in binding and vibrational energies and different space occupied by nuclear wave functions of the target ${\mathrm{H}}_{2}$ and ${\mathrm{D}}_{2}$ molecules.