title: Observation of femtosecond X-ray interactions with matter using an X-ray-X-ray pump-probe scheme.
abstract: Resolution in the X-ray structure determination of noncrystalline samples has been limited to several tens of nanometers, because deep X-ray irradiation required for enhanced resolution causes radiation damage to samples. However, theoretical studies predict that the femtosecond (fs) durations of X-ray free-electron laser (XFEL) pulses make it possible to record scattering signals before the initiation of X-ray damage processes; thus, an ultraintense X-ray beam can be used beyond the conventional limit of radiation dose. Here, we verify this scenario by directly observing femtosecond X-ray damage processes in diamond irradiated with extraordinarily intense (∼10(19) W/cm(2)) XFEL pulses. An X-ray pump-probe diffraction scheme was developed in this study; tightly focused double-5-fs XFEL pulses with time separations ranging from sub-fs to 80 fs were used to excite (i.e., pump) the diamond and characterize (i.e., probe) the temporal changes of the crystalline structures through Bragg reflection. It was found that the pump and probe diffraction intensities remain almost constant for shorter time separations of the double pulse, whereas the probe diffraction intensities decreased after 20 fs following pump pulse irradiation due to the X-ray-induced atomic displacement. This result indicates that sub-10-fs XFEL pulses enable conductions of damageless structural determinations and supports the validity of the theoretical predictions of ultraintense X-ray-matter interactions. The X-ray pump-probe scheme demonstrated here would be effective for understanding ultraintense X-ray-matter interactions, which will greatly stimulate advanced XFEL applications, such as atomic structure determination of a single molecule and generation of exotic matters with high energy densities.
authors.affiliation: Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan; RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan; inoue@x-ray.k.u-tokyo.ac.jp yabashi@spring8.or.jp.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Inoue
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan; Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Inubushi
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan;
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sato
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan; Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Tono
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan; Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Katayama
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan; Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kameshima
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan;
authors.forename: Kanade
authors.initials: K
authors.lastname: Ogawa
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan; Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Togashi
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan;
authors.forename: Shigeki
authors.initials: S
authors.lastname: Owada
authors.affiliation: Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan;
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Amemiya
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan;
authors.forename: Takashi
authors.initials: T
authors.lastname: Tanaka
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan;
authors.forename: Toru
authors.initials: T
authors.lastname: Hara
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan; Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan inoue@x-ray.k.u-tokyo.ac.jp yabashi@spring8.or.jp.
authors.forename: Makina
authors.identifier: http://orcid.org/0000-0002-2472-1684
authors.initials: M
authors.lastname: Yabashi
keywords: X-ray free-electron laser; femtosecond X-ray damage; pump–probe
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