K. Johansson

Magnetic moment of a suggested three-quasiparticle state in 125Te

The magnetic moments of the 321 keV 92− and 464 keV 52+ levels of 125Te have been determined by the PAC method to be μ = −(0.918 ± 0.032) n.m., and μ = −(0.58 ± 0.27)n.m., respectively. The result for the 321 keV level agrees with the prediction of Kisslingers three-quasiparticle model. The values of the angular correlation coefficients of the 321–177 keV and 204–177 keV cascades are, after correction for background coincidences and solid angle, A2 = −0.168 ± 0.012, A4 = −0.003 ± 0.015 and A2 = −0.403 ± 0.014, A4 = + 0.003 ± 0.020 respectively. The mixing ratio for the 204 keV (72− − 92−) transition is δ(E2/M1) = −1.88 ± 0.22 giving an E2 content of Q(E2) = 0.78 ± 0.04, while for the 321 keV (72+−92−) transition 0 ≦ Q(M2) ≦ 0.010 and −0.22 ≦ δ(M2/E1) ≦ 0. The magnetic hyperfine field for tellurium in gadolinium has been measured with the result Bhf = −38 ± 10 kG. The electric quadrupole interaction frequency of the 321 keV level for Te in Gd is ωOE = (270 ± 70)·106 rad/s.

The magnetic moment of the 32+ state in Tl203 and the question of core excitations

Abstract The nature of the 3 2 + state at 279 keV in Tl 203 is subject to a discussion based on determination of its magnetic moment. The experimental value, obtained by perturbing the angular correlation of the 401-279 γ-γ cascade, is found to be very close to the Schmidt limit. The result, μ = +0.16±0.05 n.m., from a liquid source determination, is also discussed with regard to possible systematic errors.

Transient magnetic fieldg-factor measurements of 2 1 + in64, 66, 68, 70Zn

The implantation perturbed angular correlation technique (IMPAC) has been used to determine the magnetic dipole moments of the first excited 2+ states in the stable even-even Zn-isotopes. Transient magnetic field measurements for56Fe in ferromagnetic Gd at 77 K have been performed for recoil velocities up tov/v0∼8. The result confirms the earlier reported linear velocity dependence. Theg-factors are deduced to be 0.46±0.10, 0.47±0.11, 0.46±0.14 and 0.30±0.07 for64, 66, 68Zn and70Zn respectively. The results are compared with theoretical predictions.

THE MAGNETIC MOMENT OF THE /3 over 2/

Abstract The nature of the 3 2 + state at 279 keV in Tl 203 is subject to a discussion based on determination of its magnetic moment. The experimental value, obtained by perturbing the angular correlation of the 401-279 γ-γ cascade, is found to be very close to the Schmidt limit. The result, μ = +0.16±0.05 n.m., from a liquid source determination, is also discussed with regard to possible systematic errors.

sup +

The temperature dependence of the magnetic hyperfine fields at the sites of F nuclei implanted into ferromagnetic Fe, Ni and Gd has been studied in the temperature range from 77 K to 670 K. A pulsed proton beam was used to observe the time-differential precession of the 5/2+ state in19F. Deviations from the bulk magnetization were found for Fe and Ni. The damping of the two observed fields in Ni was interpreted in terms of a field distribution caused by an induced radiation damage. The occupation sites for F and possible mechanisms of the anomalous temperature dependence are discussed.

STATE IN Tl

Abstract The gyromagnetic ratios of the first excited J π = 2 + states of 50,54 Cr, 54 Fe and 70 Ge have been determined by the ion-implantation perturbed angular correlation technique (IMPAC) with ferromagnetic Gd as stopping material. The g -factors were extracted from the measured precession angles with use of known lifetimes, static hyperfine magnetic fields and transient hyperfine magnetic field data for fast ions traversing ferromagnetic lattices. The deduced values are 0.59 ± 0.10, 0.56 ± 0.10, 1.08±0.19 and 0.38±0.08, respectively. With the exception of 54 Fe all g -factors are close to the collective value. A re-evaluation of earlier IMPAC data on 70, 72, 74, 76 Ge with Fe as stopping material has been performed. The value obtained for 70 Ge is in good agreement with the one measured in this work.

sup 203

The g-factors and half-lives of the (8−) isomer in198Pb, the 29/2− isomer in199Pb and the 19+ isomer in210At have been remeasured by the time differential perturbed angular distribution technique. A new beam pulsing equipment was used in these experiments. The results are for198Pb; g=−0.0471(8) and T1/2=4.19(10)μs, for199Pb; g=−0.0742(9) and T1/2=9.8(4) μs and for210At; g=0.698(7) and T1/2=5.9(3)μs.

AND THE QUESTION OF CORE EXCITATIONS

Gyromagnetic ratios of first 2+ states in126, 128, 130, 132Xe were determined by implantation perturbed angular correlations (IMPAC). The effective hyperfine magnetic field together with the transient magnetic field at xenon nuclei in iron was utilized to obtain the precession of the angular correlation. The precession due to the transient field was taken from systematics to be φ/g=−36±6 mrad. The effective hyperfine magnetic field was determined in an experiment on126Xe in iron to be 900±200 kG. The results for theg-factors areg(128)=0.41±0.07,g(130)=0.38±0.07 andg(132)=0.37±0.05. Theg-factor of the 2+ state in126Xe was determined in a separate experiment using a radioactive source of126I to beg(126)=0.37±0.07, and was used as calibration for the IMPAC-data.

Temperature dependence of the hyperfine fields for fluorine in ferromagnetic iron, nickel and gadolinium

Abstract The g -factors of the first 2 + levels in 102 Ru, 106 Pd and 110 Cd have been remeasured with increased accuracy, using the perturbed angular correlation method and the radio-active mother isotopes dissolved in ferromagnetic lattices. The results are g = ± 0.408 + 0.034, g = + 0.399 ± 0.029 and g = + 0.35 ± 0.07 respectively. Possible sources of error in the use of internal fields are discussed.

The g-factors of the first 2+ states in 50, 54Cr, 54Fe and 70Ge

The g-factors of the 25/2+ level at 2379.7 keV in 207Po and of the 11- level at 2702.7 keV in 208Po have been determined by the Time Differential Perturbed Angular Distribution technique (TDPAD). The results g(25/2+) = 0.433(3) and g(11-) = 1.101(13) are in good agreement with shell model predictions.