J.C. Walker

Isomer shift in the 82 keV transition of 154Sm

Abstract An isomer shift of −0.15 ± 0.09 mm/s has been observed for the 82 keV transition in 154Sm between Sm3+ and Sm2+ compounds. A value of Δ〈r 2 〉 〈r 2 〉 = 0.46 ± 0.34 × 10 −5 is deduced and compared with measured and theoretically predicted values of Δ〈r 2 〉 〈r 2 〉 in 152Sm and 154Sm.

Observation of the Mössbauer effect in238U following Coulomb excitation

Abstract Experiments performed on uranium show that the Mossbauer effect can be observed following Coulomb excitation of an actinide. There is evidence of structure in the observed spectra which may be due to quadrupole hyperfine splitting.

Lower limit on the half-life of the 113.8 level of 175Lu by the Mössbauer effect

Abstract The Mossbauer effect has been observed in the 113.8 keV transition in 175 Lu following Coulomb excitation with 3 MeV protons. A lower limit on the half-life was determined as 96±9 ps and the Debye temperature of Lu 2 O 3 was found to be 174±10° K.

Use of a Closed Cycle Helium Refrigerator for Mössbauer Studies

A closed cycle helium refrigerator has been used successfully to cool the target and absorber in Coulomb excitation Mossbauer studies. The refrigerator handles the appreciable power from the beam and may be used at any temperature above 20°K. The most severe problem of mechanical vibration has been solved.

Limits on threshold phenomena in central collisions of 12C + Pb from 1–2 GeV/n☆

Abstract Central collisions of 12 C and Pb nuclei have been examined at six beam energies from 1–2 GeV/n for possible threshold phenomena, using neutral and charged π meson production as a probe. The results indicate that although pion production increases by approximately a factor of two in this energy range, the increase is a smooth function of beam energy showing no such effects within statistical errors of ≈5% for the most central collisions.

Critical behavior of the sublattice magnetization of Dy near the Neél point

We report here the measurement of the temperature dependence of sublattice magnetization of a high quality single crystal of dysprosium metal using the Mossbauer effect. Dy‐metal is anisotropic with hexagonal close‐packed structure. Below the Neel point of about 180 K, it is antiferromagnetically ordered. No relaxation effects were observed in the spectra and it was reasonable to assume ; %a proportionality between the effective field Heff(T) and the sublattice magnetization M (T). The data were then found to satisfy the relation, M (T)/M (O) =D (1−T/TN)β within the temperature range 0.001<1‐T/TN<0.3. A careful analysis of the data yields the following values for the parameters in the above relation: TN=180.4 K, D=1.07±0.01 and β=0.335±0.01. In terms of its magnetism dysprosium metal can be considered a three‐dimensional system with two degrees of freedom for the spins. Recent model calculations seem to be particularly applicable to this system.