## Abstract

We have studied the emerging charge states [Formula Presented] and energy loss of [Formula Presented] incident ions transmitted along a [Formula Presented] axis of a [Formula Presented]-thick Si crystal. The emerging charge state distribution [Formula Presented] for well-channeled ions is governed mainly by electron impact ionization (EII). The corresponding EII cross sections were obtained by fitting the experimental [Formula Presented] with Monte Carlo simulations. For M shell ionization, they were found to be twice larger than those given by the binary encounter dipole approximation. The measured energy loss spectra were also compared to Monte Carlo simulations. The mean values and widths of these spectra increase with [Formula Presented] reflecting the increase of the stopping power S with increasing transverse energy [Formula Presented] The measured stopping for channeled ions with frozen charge state [Formula Presented] and for nonchanneled ions with charge state close to [Formula Presented] is in good agreement with theoretical estimates. Owing to the very high ion velocity, there is a significant contribution [Formula Presented] to the stopping from [Formula Presented] shell excitation even for the best channeled ions. The width and the asymmetrical shape (skewness [Formula Presented] of the energy-loss spectra depend strongly on [Formula Presented] for very well-channeled ions, [Formula Presented] for poorly channeled ions). For well-channeled ions, energy-loss spectra were reproduced by Monte Carlo simulations with the [Formula Presented] curve extracted from fitting the mean energy losses.

Original language | English |
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Pages (from-to) | 2813-2826 |

Number of pages | 14 |

Journal | Physical Review A - Atomic, Molecular, and Optical Physics |

Volume | 59 |

Issue number | 4 |

DOIs | |

Publication status | Published - 1 Jan 1999 |

## ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics