Line shifts in mass spectra of secondary ions ejected from solids by MeV-ion impact

Emission of hydrogen ions has been used to investigate the charging of the nuclear track being produced by fission fragments in organic solids. The question of interest is, if in insulating material the lifetime of ionisation along the nuclear track is sufficiently long to allow atomic motion driven by Coulomb repulsion of neighbouring ionized atoms. It is shown in this article that the hydrogen ions experience the potential produced by the ionized track core, but weaker than Auger electrons (see Schiwietz et al., Phys. Rev. Lett. 69 (1992) 628). In order to determine the mean initial energy of emission, we measured the time-of-flight distributions of secondary ions by means of a linear TOF instrument being equipped with 2 acceleration grids and converted them into axial energy distributions. Monte Carlo simulations were used to simulate the time distributions and to estimate the mean charge along the nuclear track causing the observed line shifts.