{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:1680"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:1680","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Experimental examination of ionization processes of noble gases in strong laser fields","abstract":"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.","abstract_html":"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.","abstract_has_math":false,"creators":["Wiehle, Rolf"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Helm, Hanspeter"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:22:22Z","subjects":["Doppelionisation","Bildspektrometer","Femtosekundenlaser","Tunnelionisation","Rückstreuung","double ionization","rescattering model","above threshold ionization","imaging spectrometer","tunneling"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/1680","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Helm, Hanspeter"]},{"key":"dc:creator","label":"Author","values":["Wiehle, Rolf"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Doppelionisation","Bildspektrometer","Femtosekundenlaser","Tunnelionisation","Rückstreuung","double ionization","rescattering model","above threshold ionization","imaging spectrometer","tunneling"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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.","In dieser Arbeit werden experimentelle Ergebnisse zur Wechselwirkung von intensivem Licht mit isolierten Atomen präsentiert. Im Fokus eines modernen Kurzpulslasers werden Elektrische Felder erzeugt, deren Stärke von derselben Größenordnung ist, wie die atomare Feldstärke. Die hohe Photonendichte erlaubt die Ionisation von Edelgasen durch Absorption vieler IR-Photonen, deren Einzelenergie viel kleiner ist als das Ionisationspotential. Die Wechselwirkung kann auch verstanden werden im Feld-Bild: Der Laser verbiegt das bindende Coulomb Potential, so dass das Elektron heraus tunneln kann. Die Theorie konnte die Beobachtungen für die Einzelionisation reproduzieren, für die Doppelionisation gab es deutliche Abweichungen. Das Rückstreumodell wurde entwickelt, um diese Abweichungen zu erklären. In diesem Modell wird das erste Elektron durch den Laser abgelöst und dann im oszillierenden elektrischen Feld beschleunigt. Bei der Rückkehr zum Ausgangs-Ion kann das Elektron mit diesem Wechselwirken und ein wieteres Elektron befreien. Unklar bleibt, warum Doppelionisation auch dann beobachtet wird, wenn das zurückkehrende Elektron zu lansam für eine Stoßionisation ist. Diese Arbeit untersucht die Prozesse, die der Ionisation von Edelgasen zugrunde liegen. Das Hauptaugenmerk gilt dabei der Doppelionisation, insbesondere bei Laser Intensitäten, bei denen die Rückstreuelektronen zu wenig Energie für eine weitere Ionisation haben. Der experimentelle Ansatz ist das Flugzeitmassenspektrum der Ionen und die doppelt differntielle Impulsverteilung der Photoelektronen gleichzeitig zu messen. Insbesondere die reiche Stuktur der Elektronenspektren gewährt einen Einblick in die zugrunde liegenden Prozesse."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Experimental examination of ionization processes of noble gases in strong laser fields","Experimentelle Untersuchung von Ionisationsprozessen von Edelgasen in starken Laserfeldern"]}]}],"canonical_facts":{"dc:contributor":["Helm, Hanspeter"],"dc:creator":["Wiehle, Rolf"],"dc:description.abstract":["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.","In dieser Arbeit werden experimentelle Ergebnisse zur Wechselwirkung von intensivem Licht mit isolierten Atomen präsentiert. Im Fokus eines modernen Kurzpulslasers werden Elektrische Felder erzeugt, deren Stärke von derselben Größenordnung ist, wie die atomare Feldstärke. Die hohe Photonendichte erlaubt die Ionisation von Edelgasen durch Absorption vieler IR-Photonen, deren Einzelenergie viel kleiner ist als das Ionisationspotential. Die Wechselwirkung kann auch verstanden werden im Feld-Bild: Der Laser verbiegt das bindende Coulomb Potential, so dass das Elektron heraus tunneln kann. Die Theorie konnte die Beobachtungen für die Einzelionisation reproduzieren, für die Doppelionisation gab es deutliche Abweichungen. Das Rückstreumodell wurde entwickelt, um diese Abweichungen zu erklären. In diesem Modell wird das erste Elektron durch den Laser abgelöst und dann im oszillierenden elektrischen Feld beschleunigt. Bei der Rückkehr zum Ausgangs-Ion kann das Elektron mit diesem Wechselwirken und ein wieteres Elektron befreien. Unklar bleibt, warum Doppelionisation auch dann beobachtet wird, wenn das zurückkehrende Elektron zu lansam für eine Stoßionisation ist. Diese Arbeit untersucht die Prozesse, die der Ionisation von Edelgasen zugrunde liegen. Das Hauptaugenmerk gilt dabei der Doppelionisation, insbesondere bei Laser Intensitäten, bei denen die Rückstreuelektronen zu wenig Energie für eine weitere Ionisation haben. Der experimentelle Ansatz ist das Flugzeitmassenspektrum der Ionen und die doppelt differntielle Impulsverteilung der Photoelektronen gleichzeitig zu messen. Insbesondere die reiche Stuktur der Elektronenspektren gewährt einen Einblick in die zugrunde liegenden Prozesse."],"dc:format.medium":["application/pdf"],"dc:subject":["Doppelionisation","Bildspektrometer","Femtosekundenlaser","Tunnelionisation","Rückstreuung","double ionization","rescattering model","above threshold ionization","imaging spectrometer","tunneling"],"dc:title":["Experimental examination of ionization processes of noble gases in strong laser fields","Experimentelle Untersuchung von Ionisationsprozessen von Edelgasen in starken Laserfeldern"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:22:22Z"}