Positron Mean Lives in Scandium, Yttrium, and the Rare-Earth Metals

Rodda, J.L.; Stewart, M.G.

doi:10.1103/physrev.131.255

Cited by 27 publications

(11 citation statements)

References 7 publications

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“…12 They found that the variation of the lifetime with the valence was in agreement with the predictions of Kahana. 13 As expected, they found that the lifetime in 7-cerium was consistent with a valence of 3.…”

Section: Acknowledgmentssupporting

confidence: 69%

“…12 The discrepancy was probably due to the different counter geometries used in the two experimental setups. The scintillators for the temperature measurement were about 1 in.…”

Section: Resultsmentioning

confidence: 99%

“…13 ' 18 Although Kahana did not include the effect of the lattice potential upon the conduction electrons in his computations, the application of his predictions to cerium can be justified by the close agreement between the calculated and measured variation of lifetime as a function of valency in the rare-earth metals. 12 The calculated lifetimes, assuming valences of 3, 3.5, and 4 for a-cerium, are shown in Figs. 2 and 3.…”

Section: Discussionmentioning

confidence: 99%

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Positron Annihilation inγ- andα-Cerium

1969

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similar correlation has been observed by Pierce and Blann for lighter projectiles. 5 There is not enough evidence to say whether this correlation is more than a useful fortuitous fact since the concept of an effective charge for an energetic ion in a solid is vague at best. If the electronic stopping power does follow the dependence of the mean charge of ions in gases, then differences, similar to the differences in the mean charges between I and U ions in air reported by Betz et a/. 16 (see Fig. 5), should be observable in the electronic slowing down process. Unfortunately, the present data do not cover a large enough range of reduced velocities to be sensitive to such deviations. More accurate data, taken over a wider range of energies of very heavy ions are needed in order to detect any possible dependence of the stopping process on the mass of the projectile.It is worth remarking that if the effective charge deduced from dE/dX measurements is indeed a physically meaningful quantity, then, perhaps, the potential charge experienced by the ions on their passage from 1 W. H. Zachariasen, quoted by A. W. Lawson and T. Tang, Phys. Rev. 76, 301 (1949).The 7 -> a phase transition of cerium has been investigated by measurement of the positron lifetime and angular correlation of positron-annihilation radiation in the two phases. The lifetime in the a phase was observed to be 8% shorter than the lifetime in the 7 phase when the a phase was produced by the application of pressure; and it was observed to be 5% longer when the a phase was produced by lowering the temperature. The angular correlation from a-cerium produced by pressure was observed to be slightly broader than that from 7-cerium, in contrast to the narrowing previously observed when a-cerium was produced by lowering the temperature. Since the observed changes are much smaller than predicted by models which explain the 7 -> a: transition by assuming a transfer, or partial transfer, of the 4/ electron to the conduction band, it is concluded that such electronic promotion does not occur. GUSTAFSON,McNUTT, AND ROELLIG

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Section: Acknowledgmentssupporting

confidence: 69%

“…12 The discrepancy was probably due to the different counter geometries used in the two experimental setups. The scintillators for the temperature measurement were about 1 in.…”

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Positron Annihilation inγ- andα-Cerium

1969

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“…Positron lifetimes in scandium have been measured by Rodda and Stewart (1963). Their results are consistent with three valence electrons for scandium and a density of conduction electrons per unit volume greater than that of yttrium and the lanthanide metals, which is primarily due to scandium's smaller atomic volume.…”

Section: Band Structuresupporting

confidence: 52%

Physical Metallurgy

Gschneidner¹

1975

Scandium: Its Occurrence, Chemistry Physics, Metallurgy, Biology and Technology

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“…The measured positron lifetimes in these materials ͑except for Eu and Yb͒, differ by less than 14Ϯ3 ps only. [29][30][31] However, their core momentum distributions ͑which are dominated by the 4 f contribution͒ are dramatically different. Hence, in this case, the momentum distribution can be used to characterize these materials whereas the positron lifetime cannot be so used.…”

Section: Resultsmentioning

confidence: 99%

Calculation of the Doppler broadening of the electron-positron annihilation radiation in defect-free bulk materials

et al. 2000

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Results of a calculation of the Doppler broadening of the positron-electron annihilation radiation and positron lifetimes in a large number of elemental defect-free materials are presented. A simple scheme based on the method of superimposed atoms is used for these calculations. Calculated values of the Doppler broadening are compared with experimental data for a number of elemental materials, and qualitative agreement is obtained. These results provide a database which can be used for characterizing materials and identifying impurityvacancy complexes.

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Positron Mean Lives in Scandium, Yttrium, and the Rare-Earth Metals

Cited by 27 publications

References 7 publications

Positron Annihilation inγ- andα-Cerium

Positron Annihilation inγ- andα-Cerium

Physical Metallurgy

Calculation of the Doppler broadening of the electron-positron annihilation radiation in defect-free bulk materials

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