LCLS in—photon out: fluorescence measurement of neon using soft x-rays

Obaid, Razib; Buth, Christian; Dakovski, Georgi L.; Beerwerth, R.; Holmes, Michael; Aldrich, Jeff; Lin, Ming-Fu; Minitti, Michael P.; Osipov, T.; Schlotter, W. F.; Cederbaum, Lorenz S.; Fritzsche, S.; Berrah, N.

doi:10.1088/1361-6455/aaa189

Cited by 12 publications

(17 citation statements)

References 28 publications

(44 reference statements)

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“…(1), (3) represents an a posteriori justification of the rate-equation approximation of Refs. [3,4,49,50,51]. This, in turn, assures me that the present theory describes the interaction with the light adequately.…”

Section: System-reservoir Interactionsupporting

confidence: 61%

“…However, the definition (50) is not motivated by the structure of the equations derived so far and I need to examine how this operator can be put into the expressions to remove their dependence onĴ (qp) nm (R). Equation (50) is introduced in Refs. [24,25,26,27,28,29,30,31] but not motivated and using the form (50) has consequences unaccounted for therein.…”

Section: Quantum Monte Carlo Formalismmentioning

confidence: 99%

“…[24,25,26,27,28,29,30,31] but not motivated and using the form (50) has consequences unaccounted for therein. Namely, inspecting the first line in (41), I realize that the quantum jump superoperator in terms of theĴ (qp) nm has to be expressed aŝ (50) can no longer be expressed as an operation on a state vector as before (23) but has to be written as a density operator. Let the state vector at t + δt for fixed quantum numbers p, q ∈ A el , m ∈ A…”

Section: Quantum Monte Carlo Formalismmentioning

confidence: 99%

“…If Ĥ has a matrix representation that is diagonal with respect to B, i.e., it does not couple basis states, the matrix element of the commutator in (6) vanishes. In this form, rate equations play an important role in the understanding of the ionization of atoms [3,49,50,51] and molecules [3,4] by intense light in the optical and x-ray regimes. The derivation of Eq.…”

Section: System-reservoir Interactionmentioning

confidence: 99%

“…For photoionization and Auger decay, only the charge state with the next higher electron number is involved. In the cases that two-electron emission, e.g., due to photoionization shake off or double Auger decay [49,50], are taken into account, also the charge state with the second next higher electron number enters Eq. ( 19) for n ≤ N − 2.…”

Section: Numerical Integrationmentioning

confidence: 99%

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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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Section: System-reservoir Interactionsupporting

confidence: 61%

Section: Quantum Monte Carlo Formalismmentioning

confidence: 99%

Section: Quantum Monte Carlo Formalismmentioning

confidence: 99%

Section: System-reservoir Interactionmentioning

confidence: 99%

Section: Numerical Integrationmentioning

confidence: 99%

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Dissociating diatomic molecules in ultrafast and intense light

Buth

2019

Chemical Physics

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Modeling Nonresonant X-ray Emission of Second- and Third-Period Elements without Core-Hole Reference States and Empirical Parameters

Samal

Voora

2022

J. Chem. Theory Comput.

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Nonresonant X-ray emission (XE) energies and oscillator strengths are obtained using the effective potential of the generalized Kohn–Sham semi-canonical projected random phase approximation (GKS-spRPA) method. XE energies are estimated as a difference between the valence and core ionization eigenvalues, while the oscillator strengths are obtained within a frozen orbital approximation. This straightforward approach provides accurate XE energies without any need for core-hole reference states, empirical shifting parameters, or tuning of density functionals. To account for relativistic corrections to the core orbitals, we have formulated a scalar relativistic (sr) GKS-spRPA approach based on the spin-free X2C one-electron Hamiltonian. The sr-GKS-spRPA method provides highly reliable XE energies using uncontracted basis-sets on atoms where the core-hole is created prior to emission. For the largest basis-sets used in our study, using completely uncontracted polarized core-valence Dunning basis-sets, the mean absolute errors (MAEs) are within 0.7 eV compared to experimental reference values for a test-set consisting of 27 valence-to-core XE energies of molecules with second- and third-period elements. Considering a balance of accuracy and computational effort, we recommend the use of s-uncontracted def2-TZVP for second-period and all-uncontracted def2-TZVP for third-period elements. For this recommended basis-set, the MAE is 0.2 eV. The analytically continued sr-GKS-spRPA approach, with an scriptO ( N 4 ) computational cost, enables efficient computation of XE spectra of molecules such as S8 and C60 with several core-hole states.

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Simulating X-ray Emission Spectroscopy with Algebraic Diagrammatic Construction Schemes for the Polarization Propagator

Fransson

Dreuw

2018

J. Chem. Theory Comput.

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The calculation of X-ray emission spectra has been addressed with the algebraic diagrammatic construction (ADC) scheme, using a core-ionized wave function as the reference state. With this, the valence-to-core transitions are found as the first eigenstates with negative eigenvalues. The performance of the ADC hierarchical methods ADC(2), ADC(2)-x, and ADC(3/2) has been investigated on 17 transition of second-row elements (C, N, O, F, and Ne), and 5 transitions of third-row elements (S and Cl). We report ADC(2) results within 0.20 ± 0.36 eV of experimental values with an appropriate choice of basis set and when accounting for relativistic effects, with a slight tendency toward underestimating emission energies. By comparison, ADC(2)-x yields a similar spread in relative energies, but a consistent overestimation of approximately 1.5 eV. Going to ADC(3/2), we now observe an underestimation of emission energies and a larger error spread. By comparison, calculations of X-ray absorption spectra have been reported to favor the ADC(2)-x method, with ADC(2) showing the largest error when comparing to experimental values. The difference in ADC performance trends between these core spectroscopies are attributed to the different electron rearrangement effects in X-ray absorption and emission processes.

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LCLS in—photon out: fluorescence measurement of neon using soft x-rays

Cited by 12 publications

References 28 publications

Dissociating diatomic molecules in ultrafast and intense light

Dissociating diatomic molecules in ultrafast and intense light

Modeling Nonresonant X-ray Emission of Second- and Third-Period Elements without Core-Hole Reference States and Empirical Parameters

Simulating X-ray Emission Spectroscopy with Algebraic Diagrammatic Construction Schemes for the Polarization Propagator

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