CXXIX. The alignment of Cobalt 58

Daniels, J. M.; Grace, M. A.; Halban, H.; Kürti, N.; Robinson, F. N. H.

doi:10.1080/14786441208520261

Cited by 30 publications

(7 citation statements)

References 9 publications

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“…It should be pointed out that in the nuclear alignment experiments where the results have given good agreement with the ideal theoretical case this situation has obtained. [18][19][20][21][22] In the present case, however, where B»A and g x^> g w mixing between nuclear levels does occur, and it is reasonable to suppose that if the magnitude of the interaction is comparible with the hfs, the nuclear population distribution would be modified at low temperatures in such a way as to decrease the degree of alignment. In other words, the criterion given by Bleaney, 23 that the hfs should be well resolved, is not fulfilled.…”

Section: (B) Effect Of Electron Spin-spin Interactionmentioning

confidence: 71%

“…An explanation for this can be readily found, however, if it is assumed that the gamma transition contains a small admixture of E2 radiation, for there is an interference term which produces a considerable change in the anisotropy. It should be pointed out that in previous nuclear alignment experiments, e.g., Co 60 , 18 ' 19 Co 58 , 20 Co 56 , 12 Mn 54 , 22 the final nucleus is even-even and therefore has zero spin in the ground state. Hence transitions to the ground state can never involve mixed radiation.…”

Section: (C) Interference Due To M\-e2 Mixturesmentioning

confidence: 92%

“…In the case of Nd 147 we get some reorientation but, since we have a stretched configuration (9/2-1 ->7/2), it is only very small. We may estimate the effect by using formula (20) in reference 4. We find that we would expect an attenuation of about 2% whereas we observe essentially complete attenuation.…”

Section: (D) Effect Of Reorientation In the Intermediate Statementioning

confidence: 99%

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Alignment of Three Odd-ARare-Earth Nuclei

1956

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The results of nuclear magnetic hfs alignment experiments on Ce 139 are presented, and are discussed in relation to those previously obtained for Ce 141 and Nd M7 . It is shown that the gamma-ray anisotropics, e, in the case of Ce 139 are consistent with a decay sequence 3/2 + ->5/2 + ->7/2 + , the gamma transition being Ml with ~4% admixture of E2. Even such a small admixture of E2 has an important effect upon the anisotropy through the interference term. Other factors which might affect the anisotropy are discussed: electron spin-spin interactions are important, whereas reorientation effects due to long lifetimes in the intermediate state are not. Interference is also important in the case of the 92-kev gamma ray following the decay of Nd 147 , where ^3% admixture of E2 radiation is needed to explain our results. It seems likely also that there is a similar effect in the 142-kev gamma ray following the decay of Ce 141 . The similarity of these mixtures (same magnitude and phase 4>=0) may not be fortuitous, since in each case the gamma ray connects levels which are classified by the shell model as dm and g 7 /2. In the cases of Ce 141 and Nd 147 the g 7 /2 state lies uppermost and e is reduced by the E2 admixture, whereas e is increased in Ce 139 , where the levels are inverted.

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Section: (B) Effect Of Electron Spin-spin Interactionmentioning

confidence: 71%

Section: (C) Interference Due To M\-e2 Mixturesmentioning

confidence: 92%

Section: (D) Effect Of Reorientation In the Intermediate Statementioning

confidence: 99%

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Alignment of Three Odd-ARare-Earth Nuclei

1956

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“…Bleaney et al 1 have determined the magnetic moment of Co 60 for various assumptions of the Co 60 decay scheme. Bu using their values for ju 6 Table I Table I, is not consistent with any of the modes of the Co 60 beta decay considered and at the same time a Gamow-Teller type of beta decay of Co 58 . Our determination of the MBS/ MBO ratio, however, does not decide between the two sets of /x 6 o measurements, but it shows that the separate measurements of /x 58 and /x 6 o by the Oxford workers are internally consistent.…”

mentioning

confidence: 81%

“…Daniels et al 6 have measured /i58=3.5±0.3 nm and have observed the Co 58 decay to be consistent with pure G-T selection rules. Bleaney et al 1 have determined the magnetic moment of Co 60 for various assumptions of the Co 60 decay scheme.…”

mentioning

confidence: 84%

Ratio of Magnetic Moments ofCo58andCo60

1955

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level spacing formula of the type l/D-Cexp(2E\/a) 9 using reasonable values of the coefficients c and a. The cross sections plotted in Fig. 1 are, however, not thermal neutron values, but in most cases were measured with a reactor neutron energy distribution. Corrections for epithermal resonance capture will be generally much greater for nuclei with big cross sections whose resonances are closer to thermal energies. 4 This should increase the slope of the line, but the effect is probably not very large.There seems to be a tendency for cross sections to reach a limiting value of a few thousand barns, regardless of how large the binding energy may be. This phenomenon might be due to the level separation D becoming equal to, or even less than T ra d. The problem may then be treated by continuum theory, giving

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