Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

Liu, Ji-Cai; Berrah, N.; Cederbaum, Lorenz S.; Cryan, James; Glownia, James M.; Schafer, Kenneth J.; Buth, Christian

doi:10.1088/0953-4075/49/7/075602

Cited by 15 publications

(55 citation statements)

References 68 publications

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“…To gain insights into the time-dependent quantum dynamics of the absorption of x rays and the resulting decay processes, we employ the rate-equation approximation [13,15,16,32,39] that has been used successfully in a number of studies to describe experiments, e.g., Refs. 9,12,13,15,17,31,[33][34][35][36]. Exemplary rate equations for a nitrogen atom restricted to K-shell electrons are given in Ref.…”

Section: X-ray Interaction With Neon Atomsmentioning

confidence: 99%

“…Such a time-dependent population is difficult to measure. Therefore, ion yields are considered instead which are derived from the probability at infinite time to find the atom in a specific charge state renormalized to the probability to find an ion then at all [13,15]. Ion yields are experimentally accessible via the ion time-of-flight [9,12].…”

Section: Ion Yields Of Neon Atomsmentioning

confidence: 99%

“…With x rays the sequential absorption of multiple photons [9][10][11][12][13][14][15][16] or the simultaneous absorption of two photons [17,18] are the possible processes. Even Rabi flopping [19-21] on x-ray transitions becomes feasible.…”

Section: Introductionmentioning

confidence: 99%

“…38 in the year 1973 with the Hartree-Fock-Slater approximation, little has been done with modern atomic theory. On the contrary, the description of the electronic structure in intense x-ray-atom interaction is frequently still in HartreeFock-Slater [32,39] or Dirac-Hartree-Slater [13,15,16] approximation.…”

Section: Introductionmentioning

confidence: 99%

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Neon in ultrashort and intense x-rays from free electron lasers

Buth

Beerwerth

Obaid

et al. 2018

J. Phys. B: At. Mol. Opt. Phys.

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We theoretically examine neon atoms in ultrashort and intense x rays from free electron lasers and compare our results with data from experiments conducted at the Linac Coherent Light Source (LCLS). For this purpose, we treat in detail the electronic structure in all possible nonrelativistic cationic configurations using a relativistic multiconfiguration approach. The interaction with the x rays is described in rate-equation approximation. To understand the mechanisms of the interaction, a path analysis is devised which allows us to investigate what sequences of photoionization and decay processes lead to a specific configuration and with what probability. Thereby, we uncover a connection to the mathematics of graph theory and formal languages. In detail, we study the ion yields and find that plain rate equations do not provide a satisfactory description. We need to extend the rate equations for neon to incorporate double Auger decay of a K-shell vacancy and photoionization shake off for neutral neon. Shake off is included for valence and core ionization; the former has hitherto been overlooked but has important consequences for the ion yields from an x-ray energy below the core ionization threshold. Furthermore, we predict the photon yields from xuv and x-ray fluorescence; these allow one insights into the configurations populated by the interaction with the x rays. Finally, we discover that inaccuracies in those Auger decay widths employed in previous studies have only a minor influence on ion and photon yields.Keywords: ultrashort and intense x rays, neon atom, multiconfiguration Dirac-Hartre-Fock, rate equations, free-electron laser, ion yield, photon yield I. INTRODUCTIONAtoms are the basic constituents of aggregates of matter realized in molecules, clusters, and solids. In this way, the study of the interaction of intense and ultrafast x rays with atoms is of fundamental importance for all research involving matter in such light. Intense x rays offer manifold novel perspectives for science such as diffraction experiments with single molecules [1] and x-ray quantum optics [2].Experimentally, research with intense and ultrafast x rays has only recently become a reality by the novel x-ray free electron lasers (FELs) of which there are presently four producing soft to hard x rays: the Linac Coherent Light Source (LCLS) [3,4] in Menlo Park, California, USA, the SPring-8 Angstrom Compact free electron LAser (SACLA) [5] in Sayo-cho, Sayo-gun, Hyogo, Japan, the SwissFEL [6] in Villigen, Switzerland, and the European X-Ray Free-Electron Laser (XFEL) [7] in Hamburg, Germany.The novel FEL facilities which produce x rays with unprecedented characteristics inspire one to investigate processes, known from the strong-field interaction of optical lasers with atoms, but with x rays that go be- * World Wide Web: www.christianbuth.name, electronic mail; christian.buth@web.de yond the well-established one-x-ray-photon science only possible at synchrotron light sources [8]. With x rays the sequential absorption of multiple pho...

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Section: X-ray Interaction With Neon Atomsmentioning

confidence: 99%

Section: Ion Yields Of Neon Atomsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Neon in ultrashort and intense x-rays from free electron lasers

Buth

Beerwerth

Obaid

et al. 2018

J. Phys. B: At. Mol. Opt. Phys.

Self Cite

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“…This charge rearrangement might yield different ion fragments than one would expect from the x-ray ionization of the individual constituent atoms [20,22,23]. Theoretical descriptions for these observations have been developed so far only based on phenomenological models [19,24,25]. Recently we have discovered yet another molecular effect on ionization dynamics at high x-ray intensity: The total charge for a molecule is higher than what one would expect if the molecule is treated as a collection of individual atoms [26].…”

Section: Introductionmentioning

confidence: 99%

X-ray multiphoton ionization dynamics of a water molecule irradiated by an x-ray free-electron laser pulse

et al. 2016

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We present a theoretical investigation of x-ray multiphoton ionization dynamics of polyatomic molecules, based on the rate equation model and molecular electronic structure calculations. An efficient numerical procedure is developed to calculate photoionization cross sections, Auger rates, and fluorescence rates for all possible electronic multiple-hole configurations of molecules. We investigate the charge-state distribution of a water molecule after interaction with an intense x-ray pulse and discuss its dependence on the fluence and the pulse duration of the x-ray beam. Our results demonstrate that a water molecule exposed to an intense x-ray pulse is more ionized than what would be expected within the independent-atom picture.

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Dissociating diatomic molecules in ultrafast and intense light

Buth

2019

Chemical Physics

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An ab initio theory is devised for the quantum dynamics of molecules undergoing (multiple) ionization in ultrafast and intense light. Specifically, the intertwined problem of photoionization, radiative, and electronic transitions in the course of dissociation is addressed which arises, e.g., when molecules are exposed to xuv light or x rays from free electron lasers or attosecond light sources, but the approach is equally useful in optical strong-field physics. The coherent interaction of the molecule with the light in a specific charge state is also treated. I set out from an abstract formulation in terms of the quantum optical notion of system-reservoir interaction using a master equation in Lindblad form and analyze its short-time approximation. First, I express it in a direct sum rigged Hilbert space for an efficient solution with numerical methods for systems of differential equations. Second, I derive a treatment via quantum Monte Carlo wave packet (MCWP) propagation. The formalism is concretized to diatomic molecules in Born-Oppenheimer approximation whereby molecular rotation is disregarded. The numerical integration of the master equation is carried out with a suitably factored density matrix that exploits the locality of the Hamiltonian and the Lindblad superoperator with respect to the internuclear distance. The formulation of the MCWP for molecules requires a thorough analysis of the quantum jump process; namely, the dependence on the continuous distance renders a straight wave packet promotion useless and, instead, a projected outer product needs to be employed involving an integrated quantum jump operator.

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Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

Cited by 15 publications

References 68 publications

Neon in ultrashort and intense x-rays from free electron lasers

Neon in ultrashort and intense x-rays from free electron lasers

X-ray multiphoton ionization dynamics of a water molecule irradiated by an x-ray free-electron laser pulse

Dissociating diatomic molecules in ultrafast and intense light

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