Comment on ``Dense and nanometric electronic excitations induced by swift heavy ions in an ionic CaF2crystal: Evidence for two thresholds of damage creation''

Abstract

Systematic experiments on irradiation damage in CaF${}_{2}$ were reported in a recent paper [M. Toulemonde et al., Phys. Rev. B 85, 054112 (2012)]. The measurements were performed in a broad range of ion energies and energy deposition and the inelastic thermal spike model was applied for the analysis. Here we demonstrate that contrary to what is stated in the paper, the experimental results do not prove that there is a velocity effect in CaF${}_{2}$ similar to that observed previously in Y${}_{3}$Fe${}_{5}$O${}_{12}$ and other track-forming insulators. We also show that the authors' results do not support their hypothesis that tracks are formed by quenching of a boiling phase.