Enhanced Nonlinear Double Excitation of He in Intense Extreme Ultraviolet Laser Fields

Hishikawa, Akiyoshi; Fushitani, Mizuho; Hikosaka, Y.; Matsuda, Akihiro; Liu, C.-N.; Morishita, Tōru; Shigemasa, E.; Nagasono, Mitsuru; Tono, Kensuke; Togashi, Tadashi; Ohashi, Haruhiko; Kimura, Hiroaki; Senba, Yasunori; Yabashi, Makina; Ishikawa, Tetsuya

doi:10.1103/physrevlett.107.243003

Cited by 42 publications

(32 citation statements)

References 40 publications

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“…The experimental results were simulated by solving the time-dependent Schrödinger equation for two-electrons of He whose correlations were taken into account by the hyperspherical method [2]. The simulated results reproduce the experimental spectra in Fig.…”

Section: Resultssupporting

confidence: 49%

“…The energies of the other peaks at 24 and 48 eV correspond to the two and three-photon (N=1) processes, but these are mostly due to the second and third FEL harmonics respectively, as they show only weak dependence on the FEL intensity. After the subtraction of the background signals due to the harmonics, it was found that the three-photon ionization (observed at 6.9 and 48 eV) is >20 times more efficient than the two-photon process (observed at 24 eV) at the FEL intensity of I 0 = 5 TW/cm 2 The origin of the three-photon enhancement is clear in an expanded view of the peak at 6.9 eV in Fig. 1(b).…”

Section: Resultsmentioning

confidence: 99%

“…The high collection efficiency allowed us to keep the ionization event rate low enough to avoid a space charge effect and to measure photoelectron spectra on the shot-to-shot basis [1,2]. The photoelectron spectroscopy is powerful in elucidating the non-linear processes in EUV-FEL fields, because (i) electronic states involved in the ionization process can be identified directly from the photoelectron energy and (ii) the spectral properties of fluctuating FEL pulses can be evaluated on the shot-by-shot basis.…”

Section: Epj Web Of Conferencesmentioning

confidence: 99%

“…In our previous studies [1], we have demonstrated that single-shot photoelectron spectroscopy provides detailed information on the multi-photon processes of simple atoms and molecules utilizing the inherent fluctuation of FEL pulses. Here, we apply the single shot photoelectron spectroscopy to double excitation of He in ultrashort pulse duration of EUV-FEL pulses [2]. The present study provides a route towards an efficient creation of doubly excited states of He, making it possible to investigate dynamics of strongly correlated electrons in real time.…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast Nonlinear Double Excitations of He in Intense EUV FEL Fields

Fushitani

Hikosaka

Matsuda

et al. 2013

EPJ Web of Conferences

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Section: Resultssupporting

confidence: 49%

Section: Resultsmentioning

confidence: 99%

Section: Epj Web Of Conferencesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultrafast Nonlinear Double Excitations of He in Intense EUV FEL Fields

Fushitani

Hikosaka

Matsuda

et al. 2013

EPJ Web of Conferences

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“…The high peak intensity of FELs has enabled, for the first time, studies of nonlinear effects in the VUV and soft X-ray regime, imposing new challenges for theoreticians and providing the basis for flux density limits for all other methods trying to obtain static and dynamic structural information by FELs (Wabnitz et al, 2002(Wabnitz et al, , 2005Sorokin et al, 2007;Young et al, 2010;Berrah et al, 2011;Rudek et al, 2012;Hishikawa et al, 2011;Fukuzawa et al, 2013;Tamasaku et al, 2013).…”

Section: Free-electron Lasersmentioning

confidence: 99%

The potential of future light sources to explore the structure and function of matter

Weckert¹

2014

Acta Cryst Sect A

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Structural studies in general, and crystallography in particular, have benefited and still do benefit dramatically from the use of synchrotron radiation. Lowemittance storage rings of the third generation provide focused beams down to the micrometre range that are sufficiently intense for the investigation of weakly scattering crystals down to the size of several micrometres. Even though the coherent fraction of these sources is below 1%, a number of new imaging techniques have been developed to exploit the partially coherent radiation. However, many techniques in nanoscience are limited by this rather small coherent fraction. On the one hand, this restriction limits the ability to study the structure and dynamics of non-crystalline materials by methods that depend on the coherence properties of the beam, like coherent diffractive imaging and X-ray correlation spectroscopy. On the other hand, the flux in an ultra-small diffraction-limited focus is limited as well for the same reason. Meanwhile, new storage rings with more advanced lattice designs are under construction or under consideration, which will have significantly smaller emittances. These sources are targeted towards the diffraction limit in the X-ray regime and will provide roughly one to two orders of magnitude higher spectral brightness and coherence. They will be especially suited to experiments exploiting the coherence properties of the beams and to ultra-small focal spot sizes in the regime of several nanometres. Although the length of individual X-ray pulses at a storage-ring source is of the order of 100 ps, which is sufficiently short to track structural changes of larger groups, faster processes as they occur during vision or photosynthesis, for example, are not accessible in all details under these conditions. Linear accelerator (linac) driven free-electron laser (FEL) sources with extremely short and intense pulses of very high coherence circumvent some of the limitations of present-day storage-ring sources. It has been demonstrated that their individual pulses are short enough to outrun radiation damage for single-pulse exposures. These ultra-short pulses also enable time-resolved studies 1000 times faster than at standard storage-ring sources. Developments are ongoing at various places for a totally new type of X-ray source combining a linac with a storage ring. These energy-recovery linacs promise to provide pulses almost as short as a FEL, with brilliances and multi-user capabilities comparable with a diffraction-limited storage ring. Altogether, these new X-ray source developments will provide smaller and more intense X-ray beams with a considerably higher coherent fraction, enabling a broad spectrum of new techniques for studying the structure of crystalline and non-crystalline states of matter at atomic length scales. In addition, the short X-ray pulses of FELs will enable the study of fast atomic dynamics and non-equilibrium states of matter.

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