Electronic sputtering of solid O2 by keV Ne ions

Sputtering of a solid oxygen target is studied both by experiment and by computer simulation. Experimental data of the translational energy distributions of sputtered O2 molecules are measured for 250 and 750 eV Ne impact; this process is also studied using molecular dynamics computer simulation. Translational energy distributions coincide well for high ejection energies; this proves that the collisional part of the sputtering process is well described by computer simulation. Deviations exist at the low-energy side, below around 0.3 eV; these are assigned to electronic excitations and exothermic chemical reactions that have not been included in the computer model. We show that the sputter contribution from electronic excitation is very similar to that found for 2-9 keV H2 and H3 impact and for electron impact at sub-keV energies. Our results thus allow us to separate collisional from electronic sputtering.