X-Ray Natural Circular Dichroism

Alagna, Lucilla; Prosperi, T.; Turchini, S.; Goulon, J.; Рогалев, А.; Goulon-Gìnet, C.; Natoli, C. R.; Peacock, Robert D.; Stewart, Brian

doi:10.1103/physrevlett.80.4799

Cited by 140 publications

(84 citation statements)

References 21 publications

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“…The validity of this idea was confirmed by recent experiments (Goulon eta/., 1998;Alagna et al, 1998) and calculations . We refer to Natoli et al (1998) for the full detail and complete formulas concerning XNCD.…”

Section: Introductionsupporting

confidence: 73%

Theory of X-ray natural circular dichroism

Brouder¹,

Natoli²,

Sainctavit³

et al. 1999

J Synchrotron Radiat

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A theoretical approach is presented to calculate the natural circular dichroism recently discovered in the x-ray range (XNCD). XNCD is shown to be due to an interference of electric dipole and quadrupole transitions. The basic formula represents XNCD as an odd secondrank tensor. The crystal symmetries compatible with XNCD are determined. Sum rules are derived that relate XNCD to the mixing of odd and even orbitals on the absorbing site in the ground state. A multiple-scattering theory of XNCD is presented. The results are analyzed to show that XNCD is sensitive to the relative orientation of the cluster shells. A scattering path analysis is carried out to identify the paths responsible for the signal.

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Section: Introductionsupporting

confidence: 73%

Theory of X-ray natural circular dichroism

Brouder¹,

Natoli²,

Sainctavit³

et al. 1999

J Synchrotron Radiat

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show abstract

“…If there was only one sort of atom, say right-hand, then the dq terms would lead to circular dichroism but, in the real structure, this dichroism is exactly compensated by the other sort of atom. Only the 'forbidden' reflections allow for detecting the right-left difference between the two kinds of atoms whereas the conventional X-ray optical activity is rather difficult to observe (Siddons et al, 1990;Alagna et al, 1998;Goulon et al, 1998Goulon et al, , 2000.…”

Section: Beyond the Dipole-dipole Approximationmentioning

confidence: 99%

Polarization anisotropy of X-ray atomic factors and `forbidden' resonant reflections

et al. 2005

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Symmetry and physical aspects of 'forbidden' reflections excited by a local polarization anisotropy of the X-ray susceptibility are surveyed. Such reflections are observed near absorption edges where the anisotropy is caused by distortions of the atomic electronic states owing to interaction with neighbouring atoms. As a consequence, they allow for extracting nontrivial information about the resonant atom's local environment and their physical conditions. The unusual polarization properties of the considered reflections are helpful to distinguish them from other types of 'forbidden' reflections. When such reflections are excited, it is, for example, possible to determine not only the intrinsic anisotropy of an atomic form factor but also additional anisotropy induced by thermal motion, point defects and/or incommensurate modulations. Even the local 'chirality' of atoms in centrosymmetric crystals is accessible. Unsolved key problems and possible future developments are addressed.

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“…The third generation of synchrotrons allows the measurement of these effects near the absorption edges of different elements and the study of the element-speci®c chirality. X-ray natural optical activity and circular dichroism have been tentatively investigated for many years by several authors (Siddons et al, 1990;Hart, 1994) but the corresponding effects have been unambiguously established only quite recently (Alagna et al, 1998;Goulon et al, 1998Goulon et al, , 2000. They provide non-trivial information on the fundamental properties of crystals, for example on the even±odd parity of the excited-state wave function.…”

Section: Introductionmentioning

confidence: 99%

Chirality-induced `forbidden' reflections in X-ray resonant scattering

Дмитриенко

Овчинникова

2001

Acta Cryst Sect A

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It is shown that additional Bragg re¯ections can appear exclusively owing to the local chirality associated with the left±right asymmetric environment of scattering atoms in non-magnetic crystals. The structure amplitude of these re¯ections depends on the antisymmetric part of a third-rank tensor describing the spatial dispersion effects. It enhances for resonant near-edge scattering through a mixed multipole transition, which includes a dipole±quadrupole contribution. It is shown that this mechanism works even for centrosymmetric crystals, and some realistic examples are considered in detail ( -Fe 2 O 3 , LiNbO 3 etc.). For instance, the interference between the dipole±quadrupole and quadrupole±quadrupole terms may be responsible for the threefold symmetry of the azimuthal dependence of the hhh, h = 2n + 1, re¯ections observed recently in hematite.

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X-Ray Natural Circular Dichroism

Cited by 140 publications

References 21 publications

Theory of X-ray natural circular dichroism

Theory of X-ray natural circular dichroism

Polarization anisotropy of X-ray atomic factors and `forbidden' resonant reflections

Chirality-induced `forbidden' reflections in X-ray resonant scattering

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