Multi-photon resonant effects in strong-field ionization: origin of the dip in experimental longitudinal momentum distributions

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Title Multi-photon resonant effects in strong-field ionization: origin of the dip in experimental longitudinal momentum distributions
Author Alnaser, A.S.; Maharjan, C.M.; Wang, P.; Litvinyuk, Igor
Journal Name Journal of Physics B: Atomic, Molecular and Optical Physics
Year Published 2006
Place of publication United Kingdom
Publisher Institute of Physics Publishing
Abstract We studied ionization of neon and argon by intense linearly polarized femtosecond laser pulses of different wavelengths (400 nm and 800 nm) and peak intensities, and by measuring momentum distributions of singly charged positive ions in the direction parallel to laser polarization. For Ne the momentum distributions exhibited a characteristic dip at zero momentum at 800 nm and a complex multipeak structure at 400 nm. Similarly, for Ar the momentum distributions evolved from a complex multipeak structure with a pronounced dip in the centre at 400 nm, to a smooth distribution characteristic of pure tunneling ionization (800 nm, high intensities). In the intermediate regime (800 nm, medium to low intensities), for both atoms we observed recoil ion momentum distributions modulated by quasi-periodic structures usually seen in the photoelectron energy spectra in a multi-photon regime (ATI spectra). Ne did show a characteristic 'dip' at low momentum, while the longitudinal momentum distribution for Ar exhibited a spike at zero momentum instead. The spectra did dramatically change at 400 nm, where both ions show the pronounced dip near zero momentum. Based on our results, we conclude that the structures observed in Ne and Ar momentum distributions reflect the specifics of atomic structure of the two targets and should not be attributed to effects of electron recollision, as was suggested earlier. Instead, as our results indicate, they are due to the effects of multi-photon resonant enhancement of strong-field ionization.
Peer Reviewed Yes
Published Yes
Volume 39
Page from L323
Page to L328
ISSN 0953-4075
Date Accessioned 2010-07-09
Date Available 2010-07-30T07:19:48Z
Language en_AU
Research Centre Centre for Quantum Dynamics
Faculty Faculty of Science, Environment, Engineering and Technology
Subject Atomic and Molecular Physics; Nonlinear Optics and Spectroscopy; Quantum Optics
URI http://hdl.handle.net/10072/33070
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1x

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