Monte-Carlo simulations of electronic excitations in swift heavy ion tracks in SiO2

Monte-Carlo simulations were applied for investigation of the initial electronic kinetics (' < ='10-14 s) in tracks of Ca+19 (11.4 MeV/u) in SiO2. The spatial and temporal distributions of the volume and excess energy densities of free electrons, electronic vacancies in different atomic shells and the lattice were obtained. It was demonstrated that at 10-14 s an essential part (~55%) of the energy deposited by the ion is trapped in electronic vacancies. The energy transferred to the lattice at times shorter than the characteristic time of electron-phonon coupling was determined. It was found that only ~6% of the excess energy of delocalized electrons near the projectile trajectory (~6 nm) may be thermalized on the time 10-14 s from the projectile passage. Ballistic spatial propagation of excess energy cannot be described by thermal diffusion.