Strong-Field Double Ionization of hydrogen: Wavelength Dependent Study

Igor Litvinyuk, Dipanwita Ray
James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA

Daniel Comtois, Jean-Claude Kieffer
INRS, Quebec, Canada

Asad Hasan, Ali Alnaser
American University of Sharjah, UAE

David Villeneuve
NRC, Ottawa, Canada

We studied double-ionization of H2 and D2 by intense femtosecond laser pulses of different wavelengths (500, 550, 600, 650, 800, 1300, 2000 nm) and peak intensities, by measuring kinetic energy release of resulting fragments. In addition to fragments from the well known enhanced ionization channel (5-6 eV), higher energy protons/deuterons (8-10 eV) were for the first time observed when using shorter wavelengths (500-650 nm) at high-peak intensities. This channel exhibited wavelength dependence, with KER decreasing for longer wavelengths. The channel was observed with both linear and circular polarization. We attribute this phenomenon to 3-photon excitation of molecular ion sequentially followed by the second ionization.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, and by the National Science Foundation.

Presented at DAMOP, May 2008, in State College, PA.


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