Nuclear methods for the determination of electron momentum densities in solids

Singru, R. M.

doi:10.1002/pssa.2210300102

Cited by 13 publications

(4 citation statements)

References 81 publications

(37 reference statements)

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“…and if we use them wisely they will give us comprehensive and detailed information about EMD's. Particularly useful tests of our understanding of the various methods have been provided by several recent comparative studies [9,[28][29][30]. In addition to inter-experimental comparisons there have been comparisons between experimental work and accurate theoretical profiles, the most accurate of all being for helium.…”

Section: History and Backgroundmentioning

confidence: 99%

“…Another complicating factor is the problem of exchange scattering: since both the scattered particles are electrons we must allow for the quantum mechanical exchange between them. Fortunately, to a first approximation this can be done by replacing the Rutherford cross-section by the Mott cross-section so that we have (9) The correction for exchange remains approximate however so experiments are usually set up so as to keep the correction down grazing incidence or specular reflection experiments could be used to determine the wave functions of molecules absorbed on solid surfaces and perhaps to compare surface and bulk wave functions [82]. In spite of these problems low resolution experiments on solids have been reported and McCarthy's group are hoping to carry out high resolution experiments using thin films.…”

Section: -Dimensional Distributionsmentioning

confidence: 99%

“…Unfortunately the energies are too high to make photographic films competitive but an interesting approach replaces one detector with a spark chamber [9,95,961. An annihilation photon entering the other detector triggers the high voltage supply to the spark chamber and ejects an electron to produce an ion trail in the gas of the chamber.…”

Section: -Dimensional Measurementsmentioning

confidence: 99%

“…I have tried to indicate in the text the specific points, ideas or quotations which I have taken from others. In particular, I have relied extensively on the contributions to the book "Compton Scattering" [I I] which is due to appear in print shortly, Ian McCarthy and Eric Weigold's review of (e,2e) scattering [8], Ramesh Singru's review of techniques for the study of EMD's [9] and Bill Reed's comparative study of EMD experiments [28]. In addition, a number of scientists have communicated to me most valuable ideas and suggestions and I would especially like to extend my gratitude and appreciation to Russell Bonham, Irving Epstein, Vesa Halonen, Rolf Hosemann, Sukeaki Hosoya, Seppo Manninen, Ian Mc-…”

Section: Acknowledgementsmentioning

confidence: 99%

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The Experimental Determination of Electron Momentum Densities

Williams¹

1977

Phys. Scr.

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Recent developments and the current state of experimental methods for the determination of electron momentum densities (EMD's) are reviewed. The remarkable growth both in applications of traditional techniques as well as in the development of new techniques over the last three years is described. A general analysis of the determination of EMD's in atoms, molecules and solids provides the context within which the recent work is discussed. This leads to a consideration of the physical information contained in the EMD and hence to the experimental conditions needed to ensure that the information obtained is meaningful. The potential for improving the quality of the information obtained by separating the partial contributions to the total EMD on the basis of the electron spin, orbital energy or position is discussed. The three commonly used probes, inelastic photon or electron scattering and positron annihilation are discussed in turn. Photon scattering experiments are subdivided into X-ray and γ-ray work. These techniques are well established but experiments with new sources such as Au, which emits high energy γ-rays, and synchrotrons, which provide polarized radiation, promise to open up new areas for investigation. Refinements of the technique, such as the detection of the ejected electron in coincidence with the scattered photon, are also discussed. Inelastic scattering of high energy electrons, a refinement of which is the (e,2e) technique, has been developed mainly in the last few years but is already making major contributions to the understanding of EMD's. Using both methods excellent resolution is available and the (e,2e) technique allows one to measure all three components of the EMD while at the same time separating out contributions to the total profile on the basis of orbital energies. The potential application of this technique to solids opens up many exciting possibilities. Developments in the determination of EMD's from angular correlation measurements of two photon positron annihilation are then described. Recent work in this relatively well established field includes the development of multi-counter detecting systems for the direct determination of two components of the EMD as well as the possibility of determining all three components. Other developments such as the use of polarized positrons to determine the EMD of unpaired spin electrons are also considered. The main difficulty associated with the interpretation of positron data arises from uncertainty in the analysis of the behaviour of the positron and this remains the outstanding problem. Results for specific samples obtained over the last three years using the above techniques are then described with a view to assessing the importance of EMD work as well as to providing guidance for future work.

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Section: History and Backgroundmentioning

confidence: 99%

Section: -Dimensional Distributionsmentioning

confidence: 99%

Section: -Dimensional Measurementsmentioning

confidence: 99%

Section: Acknowledgementsmentioning

confidence: 99%

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