Using a merged-beams technique, absolute total electron-capture cross sections have been measured in the thermal energy regime for collisions of ${\mathrm{Si}}^{4+}$ ions with neutral D atoms. State-of-the-art molecular-orbital coupled-channel calculations for the ${\mathrm{Si}}^{4+}$ +H(D) systems are compared to the measurements on an absolute scale. Both the existence of a surprisingly large kinematic isotope effect and an observed sharp low-energy increase of the cross section are attributed to trajectory effects due to an attractive ion-induced dipole.

• Received 6 October 1995

DOI:https://doi.org/10.1103/PhysRevA.54.R13