K. Czerski

Femtosecond dynamics: snapshots of the early ion-track evolution

The energy dissipation and femtosecond dynamics due to fast heavy ions in matter is critically reviewed with emphasis on possible mechanisms that lead to materials modifications. Starting from a discussion of the initial electronic energy-deposition processes, three basic mechanisms for the conversion of electronic into atomic energy are investigated by means of Auger-electron spectroscopy. Results for amorphous Si, amorphous C and polypropylene are presented and discussed. Experimental evidence for a highly charged track region as well as for hot electrons inside tracks is shown. As follows mainly from Auger-electron spectroscopy, there are strong indications for different track-production mechanisms in different

Si-Auger electrons from the center of nuclear tracks

Using a new ultra-high vacuum system we were able to measure ion-induced Auger electron spectra with high resolution for atomically clean amorphous Si surfaces. Measurements were performed with Ne 9þ and Ar 16þ ions at 5 MeV/u, Xe 15þ and Xe 31þ ions at 1.78 MeV/u as well as with incident electron at the two speeds, corresponding to 2.7 keV respectively 1.0 keV. The ion-induced spectra show peaks due to multiple ionization, indicating 7- or 8-fold ionization in the center of ion tracks for fast Xe ions. The Auger peaks are shifted and broadened with respect to the electron reference data. This is an indication for the nuclear-track potential and for hot electrons being present during the decay of the Auger states. 2002 Published by Elsevier Science B.V.

Spectroscopy of Si-Auger electrons from the center of heavy-ion tracks

Abstract High resolution electron spectra haven been taken for fast heavy ions at 1.78 and 5 MeV/u as well as for electrons of equal velocity incident on atomically clean Si targets. Various LVV-Auger electron structures are identified and for amorphous Si these peaks show a shift towards lower energy when the charge of the projectile is increased. This finding points to a nuclear-track potential inside the ion track. The comparison of the Auger electron spectra for amorphous Si and crystalline Si(1xa01xa01) 7×7 gives clear evidence for phase effects in the short-time dynamics of ion tracks.

Al-K-Auger energy spectra: Probing the electron dynamics in ion-solid interactions

K-Auger electron emission has been investigated for incident electrons and for different types of heavy ions interacting with mono-crystalline aluminum (100) targets at specific kinetic energies of 3 to 5 MeV/u. In an effort to gain a profound knowledge about the ionization and vacancy-decay dynamics for the K-shell in Al, spectra have been measured with different energy resolutions and angular distributions have been taken as well. Here we concentrate on the energy spectra — we identify the measured peak structures and we investigate different line intensities and mean target charge-states quantitatively, in comparison with theoretical results.