Cross sections for the emission of Lyman-$\ensuremath{\alpha}$ radiation resulting from ion---target-gas collisions have been measured for projectile energies between 1 and 25 keV. All combinations of ${\mathrm{H}}^{+}$, ${\mathrm{D}}^{+}$, $\mathrm{H}_{2}^{+}$, $\mathrm{D}_{2}^{+}$, and ${\mathrm{He}}^{+}$ projectiles on ${\mathrm{H}}_{2}$ and ${\mathrm{D}}_{2}$ targets as well as ${\mathrm{H}}^{+}$ and $\mathrm{H}_{2}^{+}$ on ${\mathrm{N}}_{2}$ have been studied. Although product excited H or D atoms which decay via the $2p\ensuremath{-}1s$ Lyman-$\ensuremath{\alpha}$-emitting transition may result from a variety of collision mechanisms, some interpretation has been possible using data from earlier experiments.