Kiyonobu Nagaya
A5035210982- Atomic and Molecular Physics
- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- Advanced X-ray Imaging Techniques
- Mass Spectrometry Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Electron and X-Ray Spectroscopy Techniques
- Advanced Electron Microscopy Techniques and Applications
- Ion-surface interactions and analysis
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Particle Accelerators and Free-Electron Lasers
- Spectroscopy and Quantum Chemical Studies
- Photocathodes and Microchannel Plates
- Enzyme Structure and Function
- Photochemistry and Electron Transfer Studies
- nanoparticles nucleation surface interactions
- High-pressure geophysics and materials
- Chalcogenide Semiconductor Thin Films
- Crystallography and Radiation Phenomena
- Diamond and Carbon-based Materials Research
- Radioactive element chemistry and processing
- Spectroscopy and Laser Applications
- Material Dynamics and Properties
- Nuclear physics research studies
Kyoto University
2015-2024
SPring-8
2014-2023
RIKEN
2019
Hyogo University
2019
Graduate School USA
2016-2017
Kyoto Notre Dame University
2016
Kumamoto University
2015
Tohoku University
2009
Nippon Soken (Japan)
2009
We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and identified that Xen+ with n up to 26 is produced at photon energy 5.5 keV. The observed high charge states (n≥24) are via five-photon absorption, evidencing the occurrence absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement experiment, elucidates...
The concept, design and performance of Japan's compact free-electron laser (FEL) facilities, the SPring-8 Compact SASE Source test accelerator (SCSS) Angstrom free electron LAser (SACLA), their applications in mainly atomic, molecular optical science are reviewed. At SCSS, intense, ultrafast FEL pulses at extreme ultraviolet (EUV) wavelengths have been utilized for investigating various multi-photon processes atoms, molecules clusters by means ion spectroscopy. quantum effect...
Ultrafast x-ray heating of clusters leads to bond contraction in the solid-to-plasma transition.
Abstract Using electron spectroscopy, we have investigated nanoplasma formation from noble gas clusters exposed to high-intensity hard-x-ray pulses at ~5 keV. Our experiment was carried out the SPring-8 Angstrom Compact free LAser (SACLA) facility in Japan. Dedicated theoretical simulations were performed with molecular dynamics tool XMDYN. We found that this unprecedented wavelength regime is a highly indirect process. In argon investigated, mainly formed through secondary cascading...
We report the first observation of electron-transfer-mediated decay (ETMD) and interatomic Coulombic (ICD) from triply charged states with an inner-valence vacancy, using Ar dimer as example. These ETMD ICD processes, which lead to fragmentation Ar(3+)-Ar into Ar(2+)-Ar(2+) Ar(3+)-Ar+, respectively, are unambiguously identified by electron-ion-ion coincidence spectroscopy in kinetic energy or electron release between two fragment ions measured coincidence.
We have investigated multiple ionization of Xe clusters by 61-nm 1011–1012 W/cm2 extreme-ultraviolet light pulses at the free-electron laser facility, SPring-8 Compact SASE Source test accelerator, in Japan, using a dead-time-free three-dimensional momentum spectrometer. It was found that average kinetic energy atomic Xe+ ions increases when increasing power density and cluster size. For these experimental conditions significant frustration photoionization occurs but no indication for...
Second-order autocorrelation spectra of XUV free-electron laser pulses from the Spring-8 Compact SASE Source (SCSS) have been recorded by time and momentum resolved detection two-photon single ionization He at 20.45 eV using a split-mirror delay-stage in combination with high-resolution recoil-ion spectroscopy (COLTRIMS). From trace we extract coherence 8 ± 2 fs mean pulse duration 28 5 fs, much shorter than estimations based on electron bunch-length measurements. Simulations within partial...
In recent years, free-electron lasers operating in the true X-ray regime have opened up access to femtosecond-scale dynamics induced by deep inner-shell ionization. We investigated charge creation and transfer context of molecular Coulomb explosion a single molecule, exposed sequential ionization within an ultrashort (10 fs) pulse. The target molecule was CH3I, methane sensitized X-rays halogenization with heavy element, iodine. Time-of-flight ion spectroscopy coincident analysis employed...
We have investigated multiphoton multiple ionization of argon and xenon atoms at 5 keV using a new x-ray free electron laser (XFEL) facility, the SPring-8 Angstrom Compact LAser (SACLA) in Japan. The experimental results are compared with theoretical presented here. absolute fluence XFEL pulse has been determined help calculations utilizing two-photon processes atom. high charge states up to +22 observed for Xe comparison point occurrence sequential L-shell absorption resonance-enabled ionization.
X-ray free-electron lasers (FELs) enable crystallographic data collection using extremely bright femtosecond pulses from microscopic crystals beyond the limitations of conventional radiation damage. This diffraction-before-destruction approach requires a new crystal for each FEL shot and, since cannot be rotated during pulse, averaging over many different and Monte Carlo integration diffraction intensities, making accurate determination structure factors challenging. To investigate whether...
We present results from an experimental ion imaging study into the fragmentation dynamics of 1-iodopropane and 2-iodopropane following interaction with extreme ultraviolet intense femtosecond laser pulses a photon energy 95 eV. Using covariance analysis, range observed pathways resulting polycations can be isolated interrogated in detail at relatively high count rates (∼12 ions shot-1). By incorporating recently developed native frames analysis approach three-dimensional procedure,...
The hitherto unexplored two-photon doubly excited states [Ne^{*}(2p^{-1}3s)]_{2} were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain rate of ICD, resulting yield Ne_{2}^{+} ions was recorded as a function delay between pump and UV probe pulses. extracted lifetimes long-lived states, 390(-130/+450)...
Abstract In high-intensity laser light, matter can be ionized by direct multiphoton absorption even at photon energies below the ionization threshold. However on tuning to lowest resonant transition, system becomes multiply excited, and more efficient, indirect pathways become operative. These mechanisms are known as interatomic Coulombic decay (ICD), where one of species de-excites its ground state, transferring energy ionize another excited species. Here we show that a higher previously...
We have investigated multiple ionization of atomic argon by extreme-ultraviolet light pulses (62 nm, 100 fs in width, <2 × 1014 W cm−2) at the free-electron laser facility Japan, and observed highly charged ions with charge state up to +6. The measured power dependence indicates that proceeds via sequential stripping electrons.
We have measured the kinetic energies of fragment ions from Ar clusters (average cluster size N~ 10?600) exposed to intense extreme ultraviolet free electron laser pulses (? ~ 61 nm, I~ 1.3? 1011 W cm?2). For small (N 200), average energy strongly increases with increasing size, indicating a promotion multiple ionization, whereas is observed be saturated for N 200. Considering how many photoelectrons can escape cluster, it was found that dependence ion exhibited frustration direct...
Using momentum-resolved electron-ion multicoincidence spectroscopy, we have investigated interatomic Coulombic decay (ICD) in the heteronuclear NeAr dimer following Ne $1s$ Auger decay. The measured intensity ratio for three ICD transitions Ne${}^{2+}$($2{s}^{\ensuremath{-}1}2{p}^{\ensuremath{-}1} {}^{1}P$)Ar to Ne${}^{2+}$($2{p}^{\ensuremath{-}2} {}^{1}S$)--Ar${}^{+}$($3{p}^{\ensuremath{-}1}$), {}^{1}D$)-Ar${}^{+}$($3{p}^{\ensuremath{-}1}$), and {}^{3}P$)Ar...
Intense X-ray free electron laser pulses can completely obliterate molecules, but the process also sheds light on energetic ions that are created. Researchers experimentally and theoretically investigate how 5-iodouacil responds to x-ray radiation.
The Coulomb explosion mechanism of a CH<sub>2</sub>I<sub>2</sub> molecule is rather different to that CH<sub>3</sub>I. kinetic energy iodine ions ∼3 times larger due repulsion the two ions, while carbon almost same for both, as indicated by red arrows represent energies atomic ions.
We studied the electronic and nuclear dynamics of I-containing organic molecules induced by intense hard X-ray pulses at XFEL facility SACLA in Japan. The interaction with pulse causes absorption multiple photons iodine atom, which results creation many vacancies (positive charges) <italic>via</italic> sequential relaxation iodine, followed intramolecular charge redistribution. In a previous study we investigated subsequent fragmentation Coulomb explosion simplest I-substituted hydrocarbon,...
The photodissociation dynamics of strong-field ionized methyl iodide were probed using intense extreme ultraviolet (XUV) radiation produced by the SPring-8 Angstrom Compact free electron LAser.
For K-shell photoionization of neon dimers, we report Ne 1s photoelectron angular distributions for Ne2++Ne+ and Ne++Ne+ channels exhibiting quite different patterns. Noninversion-symmetric patterns the former obtained by fast interatomic Coulombic decay Auger final states show direct evidence core-hole localization. Dipolar latter slow radiative other clearly that process is enough to allow dicationic dimers rotate many times before fragmentation.
A mechanism for three-photon double ionization of atoms by extreme-ultraviolet free-electron laser pulses is revealed, where in a sequential process the second step, proceeding via resonant two-photon ions, strongly enhanced excitation ionic autoionizing states. In contrast to conventional model, explains observed relative intensities photoelectron peaks and their angular dependence argon.