Electronic sputtering of LiF by Krypton (10 MeV/u): size dependent energy distributions of Li+(LiF)n clusters

A combination of imaging techniques (XY) and time-of-flight (TOF) spectroscopy was used to measure the complete velocity vector of sputtered positive secondary ions in collisions of Kr33+ (10.1 MeV/u) with well-prepared LiF single crystals in the electronic stopping regime. The energy distributions N(E) of the cluster ions (LiF) n Li+ (n ≥ 0) depend on the size of the ejecta: the maximum is slightly shifted towards lower energy with increasing cluster size n. The measured energy distributions of emitted cluster ions can be fitted by a Maxwell-Boltzmann function N(E) = AEexp(−βE). This could be an indication that the processes generating the sputtering are compatible with a thermal origin.