James Cryan
A5062905611- Laser-Matter Interactions and Applications
- Advanced X-ray Imaging Techniques
- Spectroscopy and Quantum Chemical Studies
- Advanced Chemical Physics Studies
- Advanced Electron Microscopy Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Laser-Plasma Interactions and Diagnostics
- Mass Spectrometry Techniques and Applications
- Electron and X-Ray Spectroscopy Techniques
- Photochemistry and Electron Transfer Studies
- Particle Accelerators and Free-Electron Lasers
- Atomic and Subatomic Physics Research
- Atomic and Molecular Physics
- Spectroscopy and Laser Applications
- Crystallography and Radiation Phenomena
- Advanced Fiber Laser Technologies
- Nuclear Physics and Applications
- Quantum, superfluid, helium dynamics
- Laser Design and Applications
- Molecular spectroscopy and chirality
- Random lasers and scattering media
- Photocathodes and Microchannel Plates
- Cold Atom Physics and Bose-Einstein Condensates
- Surface Chemistry and Catalysis
- Analytical Chemistry and Chromatography
SLAC National Accelerator Laboratory
2016-2025
Linac Coherent Light Source
2011-2024
Menlo School
2017-2022
Stanford Synchrotron Radiation Lightsource
2021
Stanford University
2009-2018
Lawrence Berkeley National Laboratory
2012-2016
Tullow Oil (United Kingdom)
2015
North China Electric Power University
2012
Lawrence Livermore National Laboratory
2012
Louisiana State University
2012
The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. production Ne(9+) is observed at x-ray frequencies below the Ne(8+), 1s(2) edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that combination two-photon ionization Ne(8+) ground state high-order sequential process involving single-photon transient excited states time scale faster than Auger decay. We find direct cross section orders magnitude...
Conical intersections play a critical role in excited-state dynamics of polyatomic molecules because they govern the reaction pathways many nonadiabatic processes. However, ultrafast probes have lacked sufficient spatial resolution to image wave-packet trajectories through these directly. Here, we present simultaneous experimental characterization one-photon and two-photon excitation channels isolated CF3I using gas-phase electron diffraction. In channel, mapped out real-space coherent...
Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging investigate rotation single, superfluid helium-4 containing ~10(8) 10(11) atoms. The formation vortex lattices inside confirmed by observing characteristic Bragg patterns from xenon clusters...
In quantum systems, coherent superpositions of electronic states evolve on ultrafast timescales (few femtosecond to attosecond, 1 as = 0.001 fs 10^{-18} s), leading a time dependent charge density. Here we exploit the first attosecond soft x-ray pulses produced by an free-electron laser induce core-hole excitation in nitric oxide. Using additional circularly polarized infrared pulse create clock time-resolve electron dynamics, and demonstrate control motion tuning photon energy pulse....
Attosecond-pump/attosecond-probe experiments have long been sought as the most straightforward method for observing electron dynamics in real time. Although there has much success with overlapped near-infrared femtosecond and extreme ultraviolet attosecond pulses combined theory, true attosecond-pump/attosecond-probe limited. We used a synchronized x-ray pulse pair from an free-electron laser to study electronic response valence ionization liquid water through all transient absorption...
Sequential multiple photoionization of the prototypical molecule N2 is studied with femtosecond time resolution using Linac Coherent Light Source (LCLS). A detailed picture intense x-ray induced ionization and dissociation dynamics revealed, including a molecular mechanism frustrated absorption that suppresses formation high charge states at short pulse durations. The inverse scaling average target state peak brightness has possible implications for single-pulse imaging applications.
The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These find temporal overlap pump probe pulses. strong-field dissociation generated quasi-bound dications was establish...
The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×1011 photons in ∼5 fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables vacancy Auger spectroscopy, an entirely new way study femtosecond chemical dynamics with electrons probe the local valence structure molecules near specific atomic core. Using 1.1 keV for x-ray ionization impulsively aligned molecular nitrogen, we observed rich...
We investigate the creation of double K-shell holes in N2 molecules via sequential absorption two photons on a timescale shorter than core-hole lifetime by using intense x-ray pulses from Linac Coherent Light Source free electron laser. The production and decay these states is characterized photoelectron spectroscopy Auger spectroscopy. In molecules, types core are expected, first with same N atom, second one hole each atom. report direct observations former type molecule, good agreement...
Organic chromophores with heteroatoms possess an important excited state relaxation channel from optically allowed {\pi}{\pi}* to a dark n{\pi}*state. We exploit the element and site specificity of soft x-ray absorption spectroscopy selectively follow electronic change during {\pi}{\pi}*/n{\pi}* internal conversion. As hole forms in n orbital conversion, near edge fine structure (NEXAFS) spectrum at heteroatom K-edge exhibits additional resonance. demonstrate concept nucleobase thymine,...
Time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine are used to create a movie of intramolecular motion with temporal and spatial resolution 30 fs 0.3 Å. This high fidelity is due interference between the nonstationary excitation stationary initial charge distribution. The state as local oscillator for heterodyne amplification excited distribution retrieve real-space movies atomic on ångstrom scales. has not been employed image internal in molecules...
We demonstrate a high level of laser-induced transient alignment in room temperature and density ${\text{N}}_{2}$ with technique that avoids laser field ionization. Our measured shows an improvement over previous one-pulse or two-pulse experimental results approaches the theoretical maximum value. employ eight equally spaced ultrafast pulses separation takes advantage periodic revivals for ensemble quantum rotors. Each successive pulse increases $[⟨{\text{cos}}^{2}\text{...
We present a new technique for measuring the relative delay between soft x-ray FEL pulse and an optical laser that indicates sub 25 fs RMS measurement error. An ultra-short photo-ionizes semiconductor (Si(3)N(4)) membrane changes transmission. continuum with temporally chirped bandwidth spanning 630 nm-710 nm interacts such timing of can be determined from onset spectral modulation transmitted pulse. This experiment demonstrates nearly in situ single-shot arrival time to
We measured the relative arrival time between an optical pulse and a soft x-ray from free-electron laser. This femtosecond cross-correlation measurement was achieved by observing change in reflectivity induced through absorption of fraction pulse. The main energy remained available for independent pump-probe experiment where sample may be opaque to x-rays. method employed correct two-pulse delay data canonical demonstrate 130 ± 20 fs (FWHM) temporal resolution. further analyze possible...
Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are critical element unravelling the structural dynamics matter. To fully harness this potential, we must accurately know properties: intensity, spectrum temporal profile. Owing to inherent fluctuations in free-electron lasers, mandates full characterization properties each every pulse. While diagnostics these exist, they often invasive many cannot...
We propose a scheme allowing coherent shaping, i.e., controlling both the amplitude and phase, of attosecond x-ray pulses at free-electron lasers. show that by seeding laser with short seed overfills amplification bandwidth, one can shape Wigner function pulse undulator taper profile. The examples controllable pairs trains, as well isolated spectrotemporally shaped very broad bandwidths are examined in detail. Existing lasers achieve these experimental conditions two-stage cascade, which is...
We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by self-phase stabilized 330 μJ 55 fs at 2 μm produced via difference-frequency generation a Ti:sapphire-pumped parametric amplifier. The ultrabroadband carrier-wavelength output self-compressed below 3 cycles and has 270 pulse energy. self-locked offset field preserved after filamentation. This our knowledge first...
When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding femtosecond dynamics of systems is fundamental achieving atomic resolution in flash diffraction imaging noncrystallized complex biological samples. We demonstrate capacity correlation method called "partial covariance mapping" probe neon atoms intense 8 fs pulses 1062 eV photons. A complete...