Angular dependence of the sputtering yield of water ice by 100Â keV proton bombardment

We found that the O2 emission follows a cosine dependence, as expected from isotropic collision cascades or if transport of the oxygen to the surface is by thermal diffusion. In contrast, H2O emission is more outward peaked than cosine, which could be attributed to the blocking of large angle emission by the transient crater formed during sputtering of multiple water molecules by a given projectile.