Attosecond electron wave packet interferometry

Acomplete quantum-mechanical description of matter and its interaction with the environment requires detailed knowledge of a number of complex parameters. In particular, information about

the phase of wavefunctions is important for predicting the behaviour of atoms, molecules or larger systems. In optics, information about the evolution of the phase of light in time1 and

space2 is obtained by interferometry. To obtain similar information for atoms and molecules, it is vital to develop analogous techniques. Here we present an interferometric method for

determining the phase variation of electronic wave packets in momentum space, and demonstrate its applicability to the fundamental process of single-photon ionization. We use a sequence of

extreme-ultraviolet attosecond pulses3,4 to ionize argon atoms and an infrared laser field, which induces a momentum shear5 between consecutive electron wave packets. The interferograms that

result from the interaction of these wave packets provide useful information about their phase. This technique opens a promising new avenue for reconstructing the wavefunctions6,7 of atoms

and molecules and for following the ultrafast dynamics of electronic wave packets.

This research was supported by Marie Curie Intra-European Fellowships (MEIF-CT-2004-009268, MEIF-CT-2003-500947), the Marie Curie Research Training Networks XTRA (MRTN-CT-2003-505138) and

PICNIC (HPRN-2002-00183), the Integrated Initiative of Infrastructure LASERLAB-EUROPE (RII3-CT-2003-506350) within the 6th European Community Framework Programme, the Knut and Alice

Wallenberg Foundation, the Swedish Science Council and the National Science Foundation through grant PHY-0401625. K.V. is on leave from the Department of Optics and Quantum Electronics,

University of Szeged, Szeged, Hungary. The research of Y.N., F.L., M.K., J.K. and M.J.J.V. is part of the research program of the ‘Stichting voor Fundamenteel Onderzoek der Materie (FOM)’,

which is financially supported by the ‘Nederlandse organisatie voor Wetenschappelijk Onderzoek (NWO)’. We thank T. Ruchon and M. Lewenstein for fruitful discussions.

Department of Physics, Lund University, SE-221 00 Lund, PO Box 118, Sweden

T. Remetter, P. Johnsson, K. Varjú, E. Gustafsson & A. L’Huillier

Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001, USA

FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands

Laboratoire d’Optique Appliquée, Ecole Nationale Supérieure des Techniques Avancées (ENSTA) - Ecole Polytechnique CNRS UMR 7639, 91761 Palaiseau Cedex, France

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