Anisotropy in Borrmann spectroscopy

Collins, Stephen P.; Tolkiehn, Martin; Laurus, Torsten; Дмитриенко, В. Е.

doi:10.1140/epjst/e2012-01608-1

Cited by 4 publications

(13 citation statements)

References 16 publications

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“…Reported amplitudes (6) and (7) omit factors that determine relative magnitudes, in particular radial integrals of the position variable taken between the core state and valence state. By way of an example, consider the photon energy E tuned to an L-edge, 2p.…”

Section: Natural Circular Dichroismmentioning

confidence: 99%

Superchiral photons unveil magnetic circular dichroism

Lovesey

Collins

2019

Phys. Rev. B

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Polarization-dependent photon spectroscopy (dichroism) using signal-enhancing superchiral beams is shown to be sensitive to magnetic properties of the sample, whereas previous investigations explored charge-like electronic properties of chiral samples. In the process of unveiling the potential to observe magnetic circular dichroism (MCD), we underline an affinity between spectroscopies using the Borrmann effect, twisted beams and superchiral beams. Use of an effective wavevector in a quantum-mechanical theory unites the aforementioned spectroscopies and vastly improves our understanding of their advantages. Exploiting an effective wavevector for superchiral beams, natural circular dichroism (NCD) is derived from electric dipole -magnetic dipole (E1-M1) and electric dipole -electric quadrupole (E1-E2) absorption events, and MCD is derived from electric quadrupole-electric quadrupole (E2-E2) absorption. Signal enhancement by superchiral beams is a straightforward gain for the user because NCD and MCD are otherwise precisely the same as for a circularly polarized beam, according to our calculations. Our analysis shows that enhancement of E2-E2 is superior to that available for parity-odd events under consideration. Electronic degrees of freedom in all dichroic signals are encapsulated in atomic multipoles that are frequently used in theoretical interpretations of several established experimental techniques.

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Section: Natural Circular Dichroismmentioning

confidence: 99%

Superchiral photons unveil magnetic circular dichroism

Lovesey

Collins

2019

Phys. Rev. B

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“…significant vibration of the diffracting ions. In a number of experimental reports [6,7,8], huge quadrupole enhancements at x-ray K-and L-edges are shown, along with a strong dependence on temperature.…”

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“…However, while the field intensity vanishes, the field gradient (now perpendicular to the atomic planes) persists and leads to strong quadrupole absorption (E2-E2) that dominates the recorded spectra, in the absence of significant vibration of the diffracting ions. In a number of experimental reports [6,7,8], huge quadrupole enhancements at x-ray K-and L-edges are shown, along with a strong dependence on temperature.…”

mentioning

confidence: 99%

“…Such signals include natural circular, magneto-chiral and non-reciprocal linear dichroism [3,4,5]. Recently, two processes that promise to enhance and isolate non-dipolar effects have received prominence in the literature: the Borrmann effect [6,7,8], and twisted photon beams that carry non-zero orbital angular momentum [9][10][11][12][13][14][15]. We show that these processes are very closely related, and the corresponding dichroic signals offer significant potential to advance the science of materials.The Borrmann effect, or thick crystal Laue diffraction, arises in high-quality crystals with simple chemical structures, where interference between the incident and diffracted beams sets up a standing wave-field perpendicular to the crystal planes with polarization in the plane of the diffracting atoms.…”

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confidence: 99%

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confidence: 99%

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A unified formulation of dichroic signals using the Borrmann effect and twisted photon beams

Collins

Lovesey

2018

Sci Rep

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Dichroic X-ray signals derived from the Borrmann effect and a twisted photon beam with topological charge l = 1 are formulated with an effective wavevector. The unification applies for non-magnetic and magnetic materials. Electronic degrees of freedom associated with an ion are encapsulated in multipoles previously used to interpret conventional dichroism and Bragg diffraction enhanced by an atomic resonance. A dichroic signal exploiting the Borrmann effect with a linearly polarized beam presents charge-like multipoles that include a hexadecapole. A difference between dichroic signals obtained with a twisted beam carrying spin polarization (circular polarization) and opposite winding numbers presents charge-like atomic multipoles, whereas a twisted beam carrying linear polarization alone presents magnetic (time-odd) multipoles. Charge-like multipoles include a quadrupole, and magnetic multipoles include a dipole and an octupole. We discuss the practicalities and relative merits of spectroscopy exploiting the two remarkably closely-related processes. Signals using beams with topological charges l ≥ 2 present additional atomic multipoles.

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Scanning high-sensitive x-ray polarization microscopy

et al. 2022

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We report on the realization of an extremely sensitive X-ray polarization microscope, allowing to detect tiniest polarization changes of 1 in 100 billion (10-11) with a μm-size focused beam. The extreme degree of polarization purity places the most stringent requirements on the orientation of the polarizer and analyzer crystals as well as the composition and the form fidelity of the lenses, which must not exhibit any birefringence. The results show that these requirements are currently only met by polymer lenses. Highly sensitive scanning X-ray polarization microscopy thus is established as a new method. It can provide new insights in a wide range of applications ranging from quantum electrodynamics and quantum optics to X-ray spectroscopy, materials research, and laser physics.

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Anisotropy in Borrmann spectroscopy

Cited by 4 publications

References 16 publications

Superchiral photons unveil magnetic circular dichroism

Superchiral photons unveil magnetic circular dichroism

A unified formulation of dichroic signals using the Borrmann effect and twisted photon beams

Scanning high-sensitive x-ray polarization microscopy

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