Chemical sputtering by impact of excited molecules

We study chemical sputtering of deuterated amorphous carbon surfaces by ${\rm D}$ atoms, vibrationally excited ${\rm D}_{2}$, and dissociating ${\rm D}_{3}$ molecules, in a range of impact energies, $7.5\hbox{--} 30\,{\rm eV}/{\rm D}$. We analyze the role of the internal state, i.e. the vibrationally excited and dissociating states of the neutral molecules resulting from above-surface neutralization of impacting molecular ions in typical sputtering experiments. The sputtering yields are shown to considerably increase with the internal vibrational energy at the lowest impact energies. By comparison of calculated and measured yields we draw conclusions regarding the possible mechanisms for neutralization.