Erlangen 2022 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

MO: Fachverband Molekülphysik

MO 8: Poster 1

MO 8.2: Poster

Tuesday, March 15, 2022, 16:30–18:30, P

Strong field ionization of NO₂ probed by femtosecond soft X-ray absorption spectroscopy at N K-edge — •Zhuang-Yan Zhang, Mar-Oliver Winghart, Peng Han, Carlo Kleine, Arnaud Rouzée, and Erik Nibbering — Max-Born-Institute, Berlin, Germany

The photoexcitation dynamics of NO₂ at 400 nm is investigated by time-resolved soft X-ray absorption spectroscopy using a table-top, femtosecond soft X-ray source based on high harmonic generation, which delivers femtosecond pulses in a photon energy range between 250 eV and 450 eV. The ionization dynamics of the molecule from its ground state (X²A₁) by intense 400 nm laser pulses is directly mapped into the transient change of the soft X-ray absorption spectrum near the N K-edge. Before ionization, the molecule is characterized by strong absorption features at 401 eV and 403.5 eV corresponding to transitions from the N 1s σ core-shell state to the singly occupied X²A₁ ground state and the A²B₂ first excited state of the molecule, respectively. The ionization of the molecule by the 400 nm laser pulse is accompanied for a strong depletion of the absorption observed near 401 and 403 eV, and is responsible for the appearance of new absorption lines at around 394 eV and 397 eV that we assign to fast dissociation of the molecular cation to form both NO and NO⁺ fragments. At lower intensity, these two absorption peaks are shifted by 1 eV towards lower/higher energy, indicating a strong dependence of the ionization dynamics to the laser intensity.