Energy and angle spectra of sputtered particles for low-energy deuterium impact of deuterated amorphous carbon

Abstract

We study the translational, vibrational, and rotational energy spectra of atoms and molecules reflected or sputtered from deuterated amorphous carbon surfaces by impact of low-energy (1–30 eV) deuterium atoms. Both the rovibrational and translational energies of sputtered deuterium molecules are found to be close to 1 eV over the whole impact energy range, with approximate equipartition between rotational and vibrational modes, particularly at the higher impact energies. Sputtered carbon-containing molecules are vibrationally energetic, with rovibrational energies in the range of 1.5–2.5 eV; translational and rotational motions are less energetic, close to 0.5 eV, but hotter, with more energy per degree of freedom. The energy distributions of ejected molecules confirm the partial thermalization of the impact cascade. We also study the angular spectrum of the velocity of the outgoing particles as well as their angular momentum. While the velocity vectors are described well by a cosine distribution, a preferred direction of rotation is found at the lowest energies, with the angular momenta preferentially oriented parallel to the surface.