InternalPOSTPONED: Phase-resolved attosecond photoionization
Speaker: Yann Mairesse (CELIA, Université Bordeaux I - CNRS, CEA, France)
Date: Friday, 23 April 2010 (postponed to an unknown date!)
Location: room AER19/3.11
Photoionization experiments by absorption of extreme ultraviolet radiation provide rich structural information on the considered species. In a typical experiment, synchrotron radiation is used to ionize a target. An electron wave packet is produced, which can be described as a sum of partial waves. Measuring the photoelectron angular distribution provides the relative contributions and phases of the partial waves at a given electron energy. However, to extract the evolution of the electron phase with energy (which determines the temporal structure of the electron wave packet), one needs to coherently couple two components of the wave packet with different energies. This can be achieved by two-photon two-color photoionization using high-order harmonics together with the fundamental laser field. In this talk, measurements of the photoionization of nitrogen molecules with a train of attosecond pulses together with a weak infrared field will be presented . This experiment has enabled us to measure the phase of the two-color two-photon ionization transition (molecular phase) for different states of the ion, revealing the influence of a complex resonance in the continuum. Also the ongoing extension of these experiments to the ionization of solid targets will be discussed.
