Article

High-order harmonic generation enhanced by XUV light

Max-Planck-Institut für Kernphysik, Heidelberg, Germany.
Optics Letters (Impact Factor: 3.18). 09/2011; 36(17):3530-2. DOI: 10.1364/OL.36.003530
Source: PubMed

ABSTRACT The combination of high-order harmonic generation (HHG) with resonant XUV excitation of a core electron into the transient valence vacancy that is created in the course of the HHG process is investigated theoretically. In this setup, the first electron performs a HHG three-step process, whereas the second electron Rabi flops between the core and the valence vacancy. The modified HHG spectrum due to recombination with the valence and the core is determined and analyzed for krypton on the 3d→4p resonance in the ion. We assume an 800 nm laser with an intensity of about 10(14) W/cm2 and XUV radiation from the Free Electron Laser in Hamburg (FLASH) with an intensity in the range 10(13)-10(16)W cm2. Our prediction opens perspectives for nonlinear XUV physics, attosecond x rays, and HHG-based spectroscopy involving core orbitals.

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    • "energies by the former resonance energy with respect to the first plateau ( Buth et al . , 2011 ) . The presence of originally two bound electrons is thereby crucial for the effect . Plateau extension in the presence of two electrons has already been noticed in Koval et al . ( 2007 ) , however , with a low probability of the secondary plateau . In Buth et al . ( 2011 ) , the intensity of the secondary plateau is tunable via the FEL intensity . A schematic of the proposed scheme is shown in Fig . 11 . The atoms are irradiated by both an intense optical laser field and the resonant x - ray field from an FEL . As soon as the valence electron Fig . 11 . ( Color online ) Schematic of the HHG scenario as "
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    ABSTRACT: In the past two decades high-harmonic generation (HHG) has become a key process in ultra-fast science due to the extremely short time-structure of the underlying electron dynamics being imprinted in the emitted harmonic light bursts. After discussing the fundamental physical picture of HHG including continuum--continuum transitions, we describe the experimental progress rendering HHG to the unique source of attosecond pulses. The development of bright photon sources with zeptosecond pulse duration and keV photon energy is underway. In this article we describe several approaches pointed toward this aim and beyond. As the main barriers for multi-keV HHG, phase-matching and relativistic drift are discussed. Routes to overcome these problems are pointed out as well as schemes to control the HHG process via alterations of the driving fields. Finally, we report on how the investigation of fundamental physical processes benefits from the continuous development of HHG sources.
    Advances in Atomic, Molecular, and Optical Physics 01/2012; 61. DOI:10.1016/B978-0-12-396482-3.00004-1 · 3.40 Impact Factor
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    • "For both presented schemes, we fnd substantial HHG yield for the recombination of the continuum electron with the core hole. Our prediction ofers novel prospects for nonlinear x-ray physics, attosecond x rays, and timeresolved chemical dynamics [1] [2]. "
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    ABSTRACT: Free-electron lasers are fourth-generation light sources that deliver extremely intense (>10(12) photons per pulse), ultrashort (∼10(-14) s = 10 fs) light pulses at up to kilohertz repetition rates with unprecedented coherence properties and span a broad wavelength regime from soft (∼10 eV) to hard X-ray energies (∼15 keV). They thus enable a whole suite of novel experiments in molecular physics and chemistry: Inspecting radiation-induced reactions in cold molecular ions provides unprecedented insight into the photochemistry of interstellar clouds and upper planetary atmospheres; double core-hole photoelectron spectroscopy offers enhanced sensitivity for chemical analysis; the dynamics of highly excited molecular states, pumped by vacuum ultraviolet pulses, can be inspected; and vacuum ultraviolet or X-ray probe pulses generally hold the promise to trace chemical reactions along an entire reaction coordinate with atomic spatial and temporal resolution. This review intends to provide a first overview on upcoming possibilities, emerging technologies, pioneering results, and future perspectives in this exciting field.
    Annual Review of Physical Chemistry 02/2012; 63:635-60. DOI:10.1146/annurev-physchem-032511-143720 · 15.68 Impact Factor
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