Prof. Dr. Alejandro Saenz

Prof. Saenz erforscht theoretisch das Verhalten von Atomen und Molekülen unter extremen Bedingungen — insbesondere in ultrakurzen, hochintensiven Laserpulsen und in ultrakalten Systemen. Sein aktueller Fokus liegt auf der Beschreibung von Elektronendynamik in starken Laserfeldern sowie auf präzisen quantenchemischen Berechnungen für Experimente wie KATRIN zur Neutrinomassenmessung. Die Arbeiten liefern theoretische Vorhersagen und numerische Methoden, die für Grundlagenforschung in Laserphysik, Teilchenphysik und Quantensystemen unverzichtbar sind — etwa zur Interpretation von Spektroskopie-Messungen oder zur Optimierung von Hochleistungs-Lasersystemen in Forschungsinfrastrukturen.

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• Theoretische Untersuchung von molekularem Wasserstoff in starken Laserpulsen

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 07/2003 - 06/2005 Projektleitung: Prof. Dr. Alejandro Saenz

• Highly accurate numerical treatment of the interaction of cold atoms

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 07/2003 - 08/2006 Projektleitung: Prof. Dr. Alejandro Saenz

• SFB 450 III: Ab-initio-Theorie zur Analyse und Kontrolle der Anregung, Fragmention und des Ladungstransfers in ultrakurzen Laserpulsen (Teilprojekt C 6)

  Quelle ↗

  Förderer: DFG Sonderforschungsbereich Zeitraum: 07/2004 - 06/2010 Projektleitung: Prof. Dr. Alejandro Saenz

• Improved Upper Limit on the Neutrino Mass from a Direct Kinematic Method by KATRIN

  2019

  Physical Review Letters · DOI

  We report on the neutrino mass measurement result from the first four-week science run of the Karlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. A fit of the integrated electron spectrum over a narrow interval around the kinematic end point at 18.57 keV gives an effective neutrino mass square value of (-1.0_{-1.1}^{+0.9}) eV^{2}. From this, we derive an upper limit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincides with the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurements by almost a factor of 2 and provides model-independent input to cosmological studies of structure formation.

• Strong-Field Tunneling without Ionization

  2008

  Physical Review Letters · DOI

  In the tunneling regime of strong laser field ionization we measure a substantial fraction of neutral atoms surviving the laser pulse in excited states. The measured excited neutral atom yield extends over several orders of magnitude as a function of laser intensity. Our findings are compatible with the strong-field tunneling-plus-rescattering model, confirming the existence of a widely unexplored neutral exit channel (frustrated tunneling ionization). Strong experimental support for this mechanism as origin of excited neutral atoms stems from the dependence of the excited neutral yield on the laser ellipticity, which is as expected for a rescattering process. Theoretical support for the proposed mechanism comes from the agreement of the neutral excited state distribution centered at n = 6-10 obtained from both, a full quantum mechanical and a semiclassical calculation, in agreement with the experimental results.