Study of theD++H2collision in the small-angle, low-keV energy range

A quasielastic scattering scaling law for the most probable energy loss has been derived for ion-molecule scattering, and verified for ${\mathrm{Ne}}^{+}$ and ${\mathrm{Ne}}^0$ on ${\mathrm{H}}_2$, ${\mathrm{D}}_2$ in the small-angle, low-keV energy range. This scaling is shown to break down for the more fundamental collision ${\mathrm{D}}^{+}$ + ${\mathrm{H}}_2$. The neon and ${\mathrm{D}}^{+}$ results portray the importance of the valence forces in scattering, and show a breakdown of the concept of a two-center potential for ion-molecule scattering. A single electronically inelastic channel is found for this collision. The inelastic excitation of ${\mathrm{H}}_2$ by ${\mathrm{D}}^{+}$, in the same energy and angular range, is reported to yield a sharp universal reduced cross-section plot, similar to the ${\mathrm{He}}^{+}$ + ${\mathrm{H}}_2$ collision. This supports the existence of a quasimolecule that is formed during close encounters of the collision. No strong direct dissociation of the target ${\mathrm{H}}_2$ molecule is found.