Gamma ray compton profile of aluminium

Manninen, S.; Paakkari, T.; Kajantie, K.

doi:10.1080/14786437408213561

Cited by 92 publications

(25 citation statements)

References 16 publications

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“…Since this variation with thickness is assumed to arise from the presence of multiple scattering in the data the logical step appears to be to extrapolate to zero thickness Manninen, Paakkari & Kajantie, 1974). However, it is not clear just how one should do the extrapolation, if indeed an extrapolation can be done at all, and so for this first comparison only the thinnest samples from each data set were used.…”

Section: Preliminary Comparison Of Resultsmentioning

confidence: 99%

“…The correction for the cross section arises because the scattering cross section depends on the energy of the incident and scattered radiation as well as the momentum of the scattering electron (Manninen, Paakkari & Kajantie, 1974). However, as is shown in Appendix II, if the scattering angle is 180 ° the momentum dependence of the scattering cross section is approximately 1-0.007p for all incident energies (with p in a.u.…”

Section: Correction For the Cross Section And Non-linearity Of The Momentioning

confidence: 99%

“…The differential cross section for scattering through 180 ° is (Manninen, Paakkari & Kajantie, 1974) wl A____ Z w2A2 4 d20 " w2 w2A2 + ~ -Jr- …”

Section: Momentum Dependence Of the Scattering Cross Sectionmentioning

confidence: 99%

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Commission on Spin, Charge and Momentum Density. Project No. 1. Standardization of Compton profile measurements – The Compton profile of water

Williams¹

1976

Acta Cryst Sect A

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Thirteen measurements of the Compton profile of water carried out in five different laboratories are compared. The possible sources of error inherent in Compton measurements are analysed. Inconsistent normalization of the various profiles is found to be an important source of error. After renormalization of the profiles the results are found to be consistent to within + 2 % of the peak height of the profiles. It is shown that all probable sources of error can be analysed in terms of five general types of error and further that the effects of all of these types of error on the shape of the Compton profile are almost indistinguishable from one another. The determination of the position of the Compton peak is found to be another important potential source of error in experimental measurements. Certain assumptions relating to the conversion to a momentum scale were found to be mistaken and are corrected. A comparison of currently accepted relativistic and non-relativistic expressions for the cross section revealed that they are not in fact significantly different. Multiple scattering is found to be the only major source of error which is not yet well understood. Each experimental measurement is assessed in detail with particular regard to the differences between the techniques used by the contributing groups. Proposals are made relating to the accumulation, processing and presentation of Compton data. It is concluded that a reproducibility of + 1% of the peak height of the profile is quite feasible and that in a differential experiment + 0-5 % or even better is possible.

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Section: Preliminary Comparison Of Resultsmentioning

confidence: 99%

Section: Correction For the Cross Section And Non-linearity Of The Momentioning

confidence: 99%

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Commission on Spin, Charge and Momentum Density. Project No. 1. Standardization of Compton profile measurements – The Compton profile of water

Williams¹

1976

Acta Cryst Sect A

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“…The existing Compton data on Al consists essentially of a number of measured CP's using ␥-ray sources and solid-state detectors at low momentum resolution. [27][28][29][30] Quite some time ago, Shiotani et al 31 obtained the ͓111͔ CP of Al at a momentum resolution of 0.08 a.u., but did not investigate the anisotropy of the CP or the Fermi-surface signatures therein.…”

Section: ͑1͒mentioning

confidence: 99%

High-resolution Compton scattering study of the electron momentum density in Al

et al. 2000

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We report high-resolution Compton profiles ͑CP's͒ of Al along the three principal symmetry directions at a photon energy of 59.38 keV, together with corresponding highly accurate theoretical profiles obtained within the local-density approximation ͑LDA͒ based band-theory framework. A good accord between theory and experiment is found with respect to the overall shapes of the CP's and their first and second derivatives, as well as the anisotropies in the CP's defined as differences between pairs of various CP's. There are, however, discrepancies in that, in comparison to the LDA predictions, the measured profiles are lower at low momenta, show a Fermi cutoff that is broader, and display a tail that is higher at momenta above the Fermi momentum. A number of simple model calculations are carried out in order to gain insight into the nature of the underlying 3D momentum density in Al and the role of the Fermi surface in inducing fine structure in the CP's. The present results when compared with those on Li show clearly that the size of discrepancies between theoretical and experimental CP's is markedly smaller in Al than in Li. This indicates that, with increasing electron density, the conventional picture of the electron gas becomes more representative of the momentum density and that shortcomings of the LDA framework in describing the electron correlation effects become less important.

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“…The background function is measured independently and scaled for each measurement since the functional form remains constant. The Compton cross section has been calculated in both the non-relativistic (Platzman & Tzoar, 1965) and relativistic (Eisenberger & Reed, 1974;Ribberfors, 1975;Manninen, Paakkari & Kajantie, 1974) limits but as noted by Williams (1976) the effective difference is small since the q dependence is similar. As a result of the normalization condition only the energy dependence of the factors G, X and A needs to be known and not their absolute magnitudes.…”

Section: Iib Experimental Descriptionsmentioning

confidence: 99%