Archive for Listopad, 2009

Enhanced high-order harmonics and an isolated short attosecond pulse generated by using a two-color laser and an extreme-ultraviolet attosecond pulse

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Author(s): Gang-Tai Zhang, Jie Wu, Chang-Long Xia, and Xue-Shen Liu
An efficient method to generate an isolated short attosecond pulse is presented theoretically. We show that, by adding a 0.5 fs, 62.3 nm extreme ultraviolet (xuv) attosecond pulse to a synthesized two-color field at a proper time, the harmonic intensity is effectively enhanced by 1–3 orders of mag…
[Phys. Rev. A 80, 055404] Published Mon Nov 30, 2009

Above-threshold ionization in the x-ray regime

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Author(s): Hari R. Varma, Marcelo F. Ciappina, Nina Rohringer, and Robin Santra
Two-photon above-threshold ionization processes in the x-ray regime are studied using atomic hydrogen as a model system. Within the minimal-coupling formalism of nonrelativistic quantum electrodynamics, two distinct interactions— A [over ̂] ⋅p [over ̂] in second order and A [over ̂] ^{2} in f…
[Phys. Rev. A 80, 053424] Published Mon Nov 30, 2009

Single attosecond pulse generation from aligned molecules using two-color polarization gating

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Author(s): Yongli Yu, Junjie Xu, Yuxi Fu, Hui Xiong, Han Xu, Jinping Yao, Bin Zeng, Wei Chu, J. Chen, Ya Cheng, and Zhizhan Xu
We theoretically investigate high-order harmonic generation from the diatomic molecules in an orthogonally polarized two-color few-cycle optical field by controlling the incident angle of the recolliding electron. We show that the combination of molecules and two-color polarization gating allows us …
[Phys. Rev. A 80, 053423] Published Wed Nov 25, 2009

Ionization of molecular hydrogen and deuterium by frequency-doubled Ti:sapphire laser pulses

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Author(s): Yulian V. Vanne and Alejandro Saenz
A theoretical study of the intense-field single ionization of molecular hydrogen or deuterium oriented either parallel or perpendicular to a linear-polarized laser pulse (400 nm) is performed for different internuclear separations and pulse lengths in an intensity range of (2–13)×10^{13}  W c…
[Phys. Rev. A 80, 053422] Published Wed Nov 25, 2009

Towards a theory of an attosecond transient recorder

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Author(s): E. E. Krasovskii and M. Bonitz
Laser-assisted photoemission by a chirped subfemtosecond extreme ultraviolet (xuv) pulse is considered within an exactly solvable quantum-mechanical model. Special emphasis is given to the energy dependence of photoexcitation cross section. The streaked spectra are analyzed within the classical pict…
[Phys. Rev. A 80, 053421] Published Wed Nov 25, 2009

Ultrafast Angular Momentum Orientation by Linearly Polarized Laser Fields

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Author(s): Kenta Kitano, Hirokazu Hasegawa, and Yasuhiro Ohshima
We theoretically show and experimentally verify that a pair of linearly polarized intense femtosecond pulses can create molecular ensembles with oriented rotational angular momentum on an ultrafast (∼ps) time scale, when the delay and the mutual polarization between them are appropriately arranged…
[Phys. Rev. Lett. 103, 223002] Published Tue Nov 24, 2009

Isolated sub-30-as pulse generation of an He^{+} ion by an intense few-cycle chirped laser and its high-order harmonic pulses

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Author(s): Peng-Cheng Li, Xiao-Xin Zhou, Guo-Li Wang, and Zeng-Xiu Zhao
We present an efficient method to generate a ultrashort attosecond (as) pulse when a model He^{+} ion is exposed to the combination of an intense few-cycle chirped laser pulse and its 27th harmonics. By solving the time-dependent Schrödinger equation, we found that high-order harmonic generation (H…
[Phys. Rev. A 80, 053825] Published Mon Nov 23, 2009

Electron Localization in Molecular Fragmentation of H_{2} by Carrier-Envelope Phase Stabilized Laser Pulses

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Author(s): Manuel Kremer, Bettina Fischer, Bernold Feuerstein, Vitor L. B. de Jesus, Vandana Sharma, Christian Hofrichter, Artem Rudenko, Uwe Thumm, Claus Dieter Schröter, Robert Moshammer, and Joachim Ullrich
Fully differential data for H_{2} dissociation in ultrashort (6 fs, 760 nm), linearly polarized, intense (0.44  PW/cm^{2} ) laser pulses with a stabilized carrier-envelope phase (CEP) were recorded with a reaction microscope. Depending on the CEP, the molecular orientation, and the kinetic ene…
[Phys. Rev. Lett. 103, 213003] Published Fri Nov 20, 2009

Electron transfer in fast atomic collisions in the presence of an x-ray laser

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Author(s): A. B. Voitkiv
We consider electron capture in fast collisions between a proton and hydrogen in the presence of an intense x-ray laser whose angular frequency ω is close to v^{2} /2 , where v is the collision velocity. We show that in such a case laser-induced capture becomes possible and that the latter proceeds…
[Phys. Rev. A 80, 052707] Published Wed Nov 18, 2009

Direct theoretical method for the determination of peak laser intensities from Freeman resonances in above-threshold ionization

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Author(s): Yi Wang, Jingtao Zhang, Zhizhan Xu, Yong-Shi Wu, J. T. Wang, and Dong-Sheng Guo
Freeman resonance is one of the most important phenomena in strong-field laser physics. The previous calculations to determine peak laser intensities were mainly based on solving the entire time-dependent Schrödinger equation, which requires tedious theoretical and numerical work. The newly obtaine…
[Phys. Rev. A 80, 053417] Published Tue Nov 17, 2009