Concepts in x-ray physics

Santra, Robin

doi:10.1088/0953-4075/42/2/023001

Cited by 61 publications

(75 citation statements)

References 58 publications

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“…The refraction effect could be taken into account by employing the dynamical theory of diffraction, which treats the refraction explicitly and results in a shift of Laue point that depends on the refractive index of the crystal [18]. Denote the refractive index as w = -¢ -¢¢ ( ) n n n 1 i , where ¢ < n 0 for optical photons, the refractive index has a relation with the electric susceptibility w p c = + ( ) n 1 4 [19], and χ can be determined by ab initio means for each atomic species at a given wavelength. From the detailed derivation presented in appendix B (equations (B.1)-(B.24)), as the optical photons scatter off lattice planes of inter-plane distance…”

Section: Resultsmentioning

confidence: 99%

“…We show that the frequency independent Thomson scattering stays intact for both regimes, and the frequency dependent Rayleigh scattering in the optical regime is equivalent to the dispersive corrections of form factor in the x-ray regime. We apply the Hamiltonian for photon-electron interaction under velocity gauge [19] a are the field operators for the electron and photon fields.  k , ω,   are the momentum, frequency and polarization vector of the photon.…”

Section: Appendix a Thomson And Rayleigh Scattering In The Optical Amentioning

confidence: 99%

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Radiation damage free ghost diffraction with atomic resolution

Medvedev

Chapman

et al. 2017

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

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Studies on spatial modes and the correlation anisotropy of entangled photons generated from 2D quadratic nonlinear photonic crystals X W Luo, P Xu, C W Sun et al. The x-ray free electron lasers can enable diffractive structural determination of protein nanocrystals and single molecules that are too small and radiation-sensitive for conventional x-ray diffraction. However the electronic form factor may be modified during the ultrashort x-ray pulse due to photoionization and electron cascade caused by the intense x-ray pulse. For general x-ray imaging techniques, the minimization of the effects of radiation damage is of major concern to ensure reliable reconstruction of molecular structure. Here we show that radiation damage free diffraction can be achieved with atomic spatial resolution by using x-ray parametric down-conversion and ghost diffraction with entangled photons of x-ray and optical frequencies. We show that the formation of the diffraction patterns satisfies a condition analogous to the Bragg equation, with a resolution that can be as fine as the crystal lattice length scale of several Ångstrom. Since the samples are illuminated by low energy optical photons, they can be free of radiation damage.

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Section: Resultsmentioning

confidence: 99%

Section: Appendix a Thomson And Rayleigh Scattering In The Optical Amentioning

confidence: 99%

Radiation damage free ghost diffraction with atomic resolution

Medvedev

Chapman

et al. 2017

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

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“…The basic framework can be found in Ref. [25]. All formulas below can be derived with standard angular-momentum algebra [26].…”

Section: Theory and Numerical Detailsmentioning

confidence: 99%

Interplay between relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics of Xe atoms

2017

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In this paper, we theoretically study x-ray multiphoton ionization dynamics of heavy atoms taking into account relativistic and resonance effects. When an atom is exposed to an intense x-ray pulse generated by an x-ray free-electron laser (XFEL), it is ionized to a highly charged ion via a sequence of single-photon ionization and accompanying relaxation processes, and its final charge state is limited by the last ionic state that can be ionized by a single-photon ionization. If x-ray multiphoton ionization involves deep inner-shell electrons in heavy atoms, energy shifts by relativistic effects play an important role in ionization dynamics, as pointed out in Phys. Rev. Lett. 110, 173005 (2013). On the other hand, if the x-ray beam has a broad energy bandwidth, the high-intensity x-ray pulse can drive resonant photoexcitations for a broad range of ionic states and ionize even beyond the direct one-photon ionization limit, as first proposed in Nat. Photon. 6, 858 (2012). To investigate both relativistic and resonance effects, we extend the XATOM toolkit to incorporate relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics calculations. Charge-state distributions are calculated for Xe atoms interacting with intense XFEL pulses at a photon energy of 1.5 keV and 5.5 keV, respectively. For both photon energies, we demonstrate that the role of resonant excitations in ionization dynamics is altered due to significant shifts of orbital energy levels by relativistic effects. Therefore, it is necessary to take into account both effects to accurately simulate multiphoton multiple ionization dynamics at high x-ray intensity.

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“…Within a few femtoseconds, this core hole is usually filled by an electron from an outer shell, leading to the emission of an Auger electron 1,2 , which is a highly dominant process in the case of light atoms 3 . In molecules this frequently results in formation of a repulsive state of an ion, which dissociates on a time-scale of tens to hundreds of femtoseconds.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of site-specific photochemistry following core-shell ionization of chemically inequivalent carbon atoms in acetaldehyde (ethanal)

Zagorodskikh

Eland

Zhaunerchyk

et al. 2016

The Journal of Chemical Physics

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Citation for the original published paper (version of record):Zagorodskikh, S., Eland, J H., Zhaunerchyk, V., Mucke, M., Squibb, R J. et al. (2016) Mechanisms of site-specific photochemistry following core-shell ionization of chemically inequivalent carbon atoms in acetaldehyde (ethanal). Journal of Chemical PhysicsAccess to the published version may require subscription. N.B. When citing this work, cite the original published paper. Permanent link to this version:http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301121Mechanisms of site-specific photochemistry following core-shell ionization of chemically inequivalent carbon atoms in acetaldehyde (ethanal) Site-specific fragmentation upon 1s photoionisation of acetaldehyde has been studied using synchrotron radiation and a multi-electron-ion coincidence technique based on a magnetic bottle. Experimental evidence is presented that bond rupture occurs with highest probability in the vicinity of the initial charge localisation and possible mechanisms are discussed. We find that a significant contribution to site-specific photochemistry is made by different fragmentation patterns of individual quantum states populated at identical ionisation energies.

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Concepts in x-ray physics

Cited by 61 publications

References 58 publications

Radiation damage free ghost diffraction with atomic resolution

Radiation damage free ghost diffraction with atomic resolution

Interplay between relativistic energy corrections and resonant excitations in x-ray multiphoton ionization dynamics of Xe atoms

Mechanisms of site-specific photochemistry following core-shell ionization of chemically inequivalent carbon atoms in acetaldehyde (ethanal)

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