Experimental examination of ionization processes of noble gases in strong laser fields

This thesis discusses experimental results on the interaction of intense light with isolated atoms. Inside the focus of modern pulsed lasers, electric fields are produced, which are comparable with the atomic field strength. The corresponding high number of photons available, allows the ionization of noble gas atoms by absorption of a great number of IR-photons, whose individual energy is much smaller than the atom s ionization potential. Alternatively, the interaction may be described in terms of fields: The laser modifies the binding potential, suppressing the Coulomb barrier, such that an electron may tunnel out. Theoretical calculations for single ionization were able to reproduce experimental results, but strong deviations were observed for double ionization. The rescattering model was invented which accounts for many of the previously unexplained features found in experiments. Within this model the first electron is freed by the laser and subsequently accelerated in its oscillating electric field. Upon return to its parent ion, the electron interacts with it and frees a second electron. The open question is, why double ionization is observed, even if the rescattered electron is much too slow to ionize the ion. This thesis examines the processes underlying the ionization of rare gases. The focus is on double ionization, especially at intensities, which produce rescattered electrons too slow for ionization. Our experimental approach is to record the ions time of flight and simultaneously the doubly differential momentum distribution of the photoelectrons. The latter reveals a rich structure indicate of different ionization processes.

Author dc:creator

• Wiehle, Rolf

Contributors dc:contributor

• Helm, Hanspeter

• Doppelionisation
• Bildspektrometer
• Femtosekundenlaser
• Tunnelionisation
• Rückstreuung
• double ionization
• rescattering model
• above threshold ionization
• imaging spectrometer
• tunneling

Repository record source_url

https://freidok.uni-freiburg.de/data/1680

OAI identifier oai:identifier

oai:freidok.uni-freiburg.de:1680