Large-angle elastic scattering of 59.54keV photons by Kr and Xe

Smend, F.; Czerwinski, H.

doi:10.1007/bf01384669

Cited by 15 publications

(4 citation statements)

References 7 publications

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“…Although several experiments have been carried out to measure the * yangke@sinap.ac.cn † lfzhu@ustc.edu.cn differential cross section of x-ray elastic scattering of noble gases [5][6][7], the detectors used in these works, i.e., the intrinsic Ge planar detector [5,6] and the scintillation counter [7], have an energy resolution of only about several hundred eV, which may resolve the elastic scattering and the Compton scattering at large scattering angles, but they cannot resolve the elastic scattering and inelastic excitations because the excitation energy of the valence shell transition of atoms and molecules is less than 25 eV, which is much less than the energy resolution of these detectors. Furthermore, the ionization continuum also contributes to the elastic scattering in these experiments due to the same reason.…”

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Determination of the electronic structure of atoms and molecules in the ground state: Measurement of molecular hydrogen by high-resolution x-ray scattering

Liu

Mei

et al. 2014

Phys. Rev. A

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The high-resolution x-ray-scattering technique is used to study the elastic scattering of atoms and molecules in the gas phase. The elastic squared form factor, which is the square of the Fourier transformation of the electron density distribution in position space and reveals the pure electronic structure of atoms and molecules in the ground state, of molecular hydrogen is measured at an incident photon energy of about 9889 eV and an energy resolution of about 70 meV. Although it is generally thought that the x-ray-scattering technique is identical to high-energy electron scattering, at least for elastic scattering these two techniques have an apparent difference, i.e., the pure electronic structure of a molecule in the ground state can be determined by x-ray scattering while it cannot be obtained by the high-energy electron impact method due to the interference between the scattering of separate nuclei and of the electrons in the target. The present experimental results match the theoretical calculations very well, which demonstrates that high-resolution x-ray scattering is a powerful tool to study the electronic structure of atoms and molecules in the ground state.

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Determination of the electronic structure of atoms and molecules in the ground state: Measurement of molecular hydrogen by high-resolution x-ray scattering

Liu

Mei

et al. 2014

Phys. Rev. A

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“…Examples are the nonrelativistic [12] and relativistic [13] nonlocal FF and ISF of Hubbell et al Beyond the IPA, some results for FF and ISF exist [14][15][16]. Other corrections include the anomalous scattering factor (ASF) for Rayleigh scattering and the coherent nuclear Thomson (NT) amplitude.Very few experiments have been reported for scattering from free atoms [17][18][19][20], the case for which cross sections are usually calculated. In view of the basic need for accurate and absolute measurements in free atoms to assess the importance of various approximations, we have explored scattering from neon at 90 ± in the 11 to 22 keV range where sizable differences (up to 16%) between the S-matrix and nonlocal exchange form-factor calculations of the elastic scattering channel exist.…”

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confidence: 99%

“…Very few experiments have been reported for scattering from free atoms [17][18][19][20], the case for which cross sections are usually calculated. In view of the basic need for accurate and absolute measurements in free atoms to assess the importance of various approximations, we have explored scattering from neon at 90 ± in the 11 to 22 keV range where sizable differences (up to 16%) between the S-matrix and nonlocal exchange form-factor calculations of the elastic scattering channel exist.…”

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Manifestations of Nonlocal Exchange, Correlation, and Dynamic Effects in X-Ray Scattering

et al. 1998

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We report precise measurements of differential x-ray scattering cross sections in Ne and He from 11 -22 keV and develop a method for obtaining predictions of comparable accuracy (1%). The measurement of ratios (total scattering in Ne to He and Compton to Rayleigh scattering in Ne) facilitates comparison to theories. We find evidence for the need to include nonlocal exchange, electron correlation, and dynamic effects for an accurate description at low Z and conclude that no single current theory is sufficient. [S0031-9007(98)06921-X] PACS numbers: 32.80.Cy, 07.85. -mThe use of x rays has been of fundamental importance in a number of fields, from demonstrating the validity of the quantum theory of radiation [1] to determining macromolecular structures such as DNA [2]. Recent advances in experimental techniques, such as the use of modern synchrotron sources that permit accurate experiments with well-defined initial conditions, coupled with similar advances in theory, such as the development of computer codes that calculate the relativistic S-matrix, now make it possible to perform precision investigations necessary to probe details in the description of atomic x-ray scattering. Among the phenomena that have recently been investigated are the need for multipoles in describing photon-atom interactions [3] and the effects of electron correlations on atomic processes ([4], and references therein). In this Letter we describe the need for nonlocal effects in describing x-ray scattering, even at relatively high energies, and confirm the need for inclusion of electron correlation and dynamic effects. In obtaining these results, we performed the first experimental decomposition of Compton scattering from Rayleigh scattering in free atoms. We also describe experimental and theoretical methods to obtain absolute scattering cross sections at an accuracy of ഠ1%. Our results have broad implications for calculations of elastic and inelastic photon scattering from light elements, which are widely used to determine crystallographic structures and electron momentum distributions.Relativistic S-matrix calculations of elastic photon scattering have been available for some time [5]. These have mainly been tested by high energy x-or g-ray scattering on solid targets composed of heavy elements [6] where they are superior to other, simpler techniques, leading to their wide acceptance as a benchmark [7]. Only recently [8] has a similar theory been successfully applied to Compton scattering. This theory has not been as extensively tested against measurements. In both cases, the emphasis has been on an accurate description of the photon-atom interaction. The main approximations are made in the description of the atom, which is assumed to be spherically symmetric and with the electron-electron interactions included only within the independent particle (IPA) and local exchange approximations.Simpler predictions for these cross sections can be obtained by calculating form factors (FF) for Rayleigh scattering, and Compton profiles, using the impu...

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“…, [15,16] In a previous work [14], it was demonstrated that the real anomalous scattering factors f'(co) calculated by Cromer and I.iberman [17,18] "p, {r)sin(qr)r' g;(q)=4m (4) 0 g'(~) = fci (~) -fci (~) . (7) As shown earlier [14] Relativistic second-order S-matrix calculations were carried out in the cases of relatively strongly bound or "inner" subshells for which the ratio of photon energy to the subshell binding energy was less than 300. This condition is satisfied in the case of tantalum for example by EC, L, M, and N, to N3 subshells.…”

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confidence: 99%