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MO: Molekülphysik

MO 12: Ultrafast Structural Changes

MO 12.6: Vortrag

Montag, 13. März 2006, 15:30–15:45, H12

Multi-Photon Ionization of Molecular Nitrogen by Femtosecond Soft X-ray FEL Pulses — •Mathias Richter¹, Andrei A. Sorokin^1,2, Sergey V. Bobashev², and Kai Tiedtke³ — ¹Physikalisch-Technische Bundesanstalt, PTB, Abbestrasse 2-12, D-10587 Berlin, Germany — ²Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia — ³Deutsches Elektronensynchrotron, DESY, Notkestrasse 85, D-22603 Hamburg, Germany

At the new free-electron laser (FEL) for vacuum ultraviolet (VUV) and soft X-ray radiation of the Deutsches Elektronensynchrotron (DESY) in Hamburg, multi-photon double ionization of molecular nitrogen was observed and studied by ion time-of-flight spectroscopy. The experiments were performed at the microfocus beamline BL2 of the VUV-FEL with photon pulses of estimated 25-fs duration and irradiance levels up to 20 Terrawatt per square centimeter at a photon energy of 38 eV. Emphasis was laid on the determination of absolute photon numbers per pulse with the help of a calibrated setup which allows the investigation of non-linear effects by quantitative measurements. Results are discussed in terms of a sequential double photoionization scheme.