Narrow-band hard-x-ray lasing with highly charged ions

Lyu, Chunhai; Cavaletto, Stefano M.; Keitel, Christoph H.; Harman, Z.

doi:10.1038/s41598-020-65477-0

Cited by 14 publications

(5 citation statements)

References 95 publications

(163 reference statements)

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“…By knowing these field correlation functions for stochastic FEL pulses, one can predict the properties of C(ω s1 , ω s2 , T ) and retrieve spectroscopic information. Suitable methods have long been utilized to model experiments with stochastic XFEL pulses (143)(144)(145)(146)(147)(148) and simulate chaotic pulses with the correct statistical properties. Figure 7a,b depicts simulated temporal and spectral profiles of stochastic FEL pulses based on the model in References 51, 144, and 145, along with their average intensity profiles.…”

Section: Covariance Signals With Stochastic X-ray Free-electron Lasersmentioning

confidence: 99%

Ultrafast X-Ray Probes of Elementary Molecular Events

Keefer

Cavaletto

Rouxel

et al. 2023

Annu. Rev. Phys. Chem.

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Elementary events that determine photochemical outcomes and molecular functionalities happen on the femtosecond and subfemtosecond timescales. Among the most ubiquitous events are the nonadiabatic dynamics taking place at conical intersections. These facilitate ultrafast, nonradiative transitions between electronic states in molecules that can outcompete slower relaxation mechanisms such as fluorescence. The rise of ultrafast X-ray sources, which provide intense light pulses with ever-shorter durations and larger observation bandwidths, has fundamentally revolutionized our spectroscopic capabilities to detect conical intersections. Recent theoretical studies have demonstrated an entirely new signature emerging once a molecule traverses a conical intersection, giving detailed insights into the coupled nuclear and electronic motions that underlie, facilitate, and ultimately determine the ultrafast molecular dynamics. Following a summary of current sources and experiments, we survey these techniques and provide a unified overview of their capabilities. We discuss their potential to dramatically increase our understanding of ultrafast photochemistry.

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Section: Covariance Signals With Stochastic X-ray Free-electron Lasersmentioning

confidence: 99%

Ultrafast X-Ray Probes of Elementary Molecular Events

Keefer

Cavaletto

Rouxel

et al. 2023

Annu. Rev. Phys. Chem.

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“…Early optical-laser experiments were also performed with the chaotic pulses available at the time, and simula-tion techniques were developed to model their properties [38]. These methods have long been utilized to model experiments at x-ray FELs [39][40][41][42][43][44]. Pfeifer et al showed that, by using a model starting from random spectral phases, one can simulate chaotic pulses with the correct statistical properties of SASE FEL pulses, including their time and frequency spiky profiles and their energy distribution [40].…”

Section: Modeling Of Stochastic X-ray Free-electron-laser Pulsesmentioning

confidence: 99%

High temporal and spectral resolution of stimulated x-ray Raman signals with stochastic free-electron-laser pulses

Cavaletto,

Keefer,

Mukamel

2021

Preprint

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The chaotic nature of x-ray free-electron-laser pulses is a major bottleneck that has limited the joint temporal and spectral resolution of spectroscopic measurements. We show how to use the stochastic x-ray field statistics to overcome this difficulty by correlation signals averaged over independent pulse realizations. No control is required over the spectral phase of the pulse, enabling immediate application with existing, noisy x-ray free-electron-laser pulses. The proposed stimulated Raman technique provides the broad observation bandwidth and high time-frequency resolution needed for the observation of elementary molecular events. A model is used to simulate chaotic freeelectron-laser pulses and calculate their correlation properties. The resulting joint temporal/spectral resolution is exemplified for a molecular model system with time-dependent frequencies and for the RNA base Uracil passing through a conical intersection. Ultrafast coherences, which represent a direct signature of the nonadiabatic dynamics, are resolved. The detail and depth of physical information accessed by the proposed stochastic signal are virtually identical to those obtained by phase-controlled pulses. I. INTRODUCTIONRecent advances in the generation of sub-femtosecond extreme-ultraviolet (XUV) and x-ray pulses are enabling the control of electron dynamics on their natural time scales [1][2][3][4]. This is essential for the direct manipulation of the ensuing electronic and nuclear dynamics and for the control of chemical reactions with light, with broad applications to photochemistry and photobiology [5][6][7].Free-electron lasers (FELs) provide intense pulses at frequencies ranging from the XUV to the hard-x-ray domain [2] suitable for nonlinear x-ray spectroscopy [8]. While XUV seeded FELs offer stable coherent XUV pulses [9] with the possibility of pulse shaping [10] and control [11], soft-and hard-x-ray FELs based on the selfamplified spontaneous emission (SASE) mechanism [12] provide stochastic pulses with limited longitudinal coherence, and noisy spikes in their temporal and spectral profiles. Stimulated x-ray Raman scattering, a fundamental building block of nonlinear spectroscopy [13], was recently demonstrated using hard-x-ray FEL pulses [14], but future multidimensional nonlinear x-ray spectroscopy protocols [15-17] require coherent and reproducible pulses. Self-or laser-seeding methods have been implemented to improve the coherence of hard-x-ray FEL pulses [18]. Novel techniques have demonstrated highintensity few-femtosecond pulses [19] with reduced intensity spikes [20], but with an underlying SASE structure which renders them not reproducible from shot to shot. Recently, transient redistribution of ultrafast electronic coherences in attosecond Raman signals (TRUE-CARS) [21] was proposed as a suitable technique to achieve the demanding time-frequency resolution nec-

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“…( 6) (the term S) can be modeled as a Gaussian white noise following the guidelines of Ref. [16], an approach followed later by others [17,18]. The interest of this approach is that it provides the correct spectral behavior for the field [16].…”

Section: Incident Source -Spontaneous Emissionmentioning

confidence: 99%

“…It is well-known that this problem can be overcome by adding a phenomenological fluctuating polarization source that simulates spontaneous emission. Compared with many calculations of x-ray lasing in gas or plasmas (see for instance Refs [15][16][17][18]) short spatial scales involved in this multilayer context, do not permit the use of the slowly varying envelope approximation so that basic Maxwell equations have to be solved directly. This is done here using the so-called Finite-Difference-Time-Domain (FDTD) method [19].…”

Section: Introductionmentioning

confidence: 99%

Maxwell-Bloch modeling of an x-ray pulse amplification in a 1D photonic crystal

Peyrusse,

Jonnard,

André

2020

Preprint

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We present an implementation of the Maxwell-Bloch (MB) formalism for the study of x-ray emission dynamics from periodic multilayer materials whether they are artificial or natural. The treatment is based on a direct Finite-Difference-Time-Domain (FDTD) solution of Maxwell equations combined with Bloch equations incorporating a random spontaneous emission noise. Besides periodicity of the material, the treatment distinguishes between two kinds of layers, those being active (or resonant) and those being off-resonance. The numerical model is applied to the problem of Kα emission in multilayer materials where the population inversion could be created by fast inner-shell photoionization by an x-ray free-electron-laser (XFEL). Specificities of the resulting amplified fluorescence in conditions of Bragg diffraction is illustrated by numerical simulations. The corresponding pulses could be used for specific investigations of non-linear interaction of x-rays with matter.

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Narrow-band hard-x-ray lasing with highly charged ions

Cited by 14 publications

References 95 publications

Ultrafast X-Ray Probes of Elementary Molecular Events

Ultrafast X-Ray Probes of Elementary Molecular Events

High temporal and spectral resolution of stimulated x-ray Raman signals with stochastic free-electron-laser pulses

Maxwell-Bloch modeling of an x-ray pulse amplification in a 1D photonic crystal

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