Seminars

PIER Photon Science Colloquium: Multidimensional XUV spectroscopy of 2-electron dynamics and Fano-phase control

by Thomas Pfeifer (Max-Planck Institut für Kernphysik, Heidelberg)

Friday, July 5, 2013 from to (Europe/Berlin)
at DESY Hamburg ( CFEL Lecture Hall, Bldg. 99 )
Description One of the most intriguing aspects of physics is that far-reaching consequences can emerge from the study of small, fundamental, yet not fully understood, systems.  For example, the motion of two interacting particles in the attractive potential of a third constitutes a realization of the time-dependent three-body problem, defying analytical solution.
Here in this talk, I will focus on helium atoms to explore fundamental time-dependent two-electron dynamics.  The technological key is our experimental development of nonlinear coherent absorption spectroscopy with extreme ultraviolet (XUV) light at high spectral resolution.  Doubly-excited He states are prepared by attosecond-pulsed XUV light and modified or probed by few-cycle near-visible pulses with tunable intensity and time delay after excitation.  This approach creates a multidimensional XUV spectroscopy method, which is sensitive to field-induced couplings of short-lived autoionizingstates and their complex-valued time-dependent coefficients.
In addition to the reconstruction of a correlated two-electron wave packet, the natural Fanoresonance phenomenon is observed and controlled by the interaction with the laser field.  From these results, we extract a general closed-form universal mapping that links the Fanoq parameter to the laser-controllable phase of a quantum state and its dipole response, with a large range of future applications.