J. Dupák

Nuclear orientation of156Tb in gadolinium matrix

The anisotropy of the angular distribution of gamma-rays from the decay of156Tb, oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction in the range of temperatures from 14·6 to 68·4 mK. The temperature dependence of anisotropy was measured for the first time. The parameters of hyperfine magnetic dipole and electric quadrupole splittings have been determined and the values of the magnetic dipole moment ¦Μ156¦=(9·6±1·3)×10−27 J/T and the electric quadrupole momentQ156=(2·9±0·9)×10−28 m2 of the156Tb ground state have been calculated. Multipole mixing ratios andB(E2) branching ratios of many gamma-ray transitions occurring in156Gd have been found and the results have been discussed in terms of the rotational-vibration and pairing-plus-quadrupole models.

Nuclear orientation studies of the 51·5 min167Lu decay

Anisotropies of γ rays emitted in the decay of167Lu,T1/2=51·5 min, were measured. The167Lu was oriented by the hyperfine interaction when the lutetium activity was included in a gadolinium host which was cooled to 15 mK temperature. A top-loading3He∶4He dilution refrigerator capable of quickly cooling a short-lived sample was used. Multipole mixing ratios have been evaluated for many transitions. The spin assignments have been made for a number of levels in167Yb and their parities have been deduced. In particular, an unambiguous 11/2− assignment was made for the 571·5 keV level which was identified as the band head of the 11/2− [505] band observed by Lindblad. The rotational bands in167Yb are discussed.

Nuclear orientation of152,154Tb in gadolinium

The anisotropy in the directional distribution of gamma-rays from the decay of152,154Tb oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction at temperature of (15±1) mK. Unambiguous values of spin have been deduced for several levels in152Gd. Multipole mixing ratios of many gamma-ray transitions occurring in152Gd have been found and results are compared with the similar transitions in150,154,156Gd and they are discussed in terms of the rotational-vibrational model and dynamic deformation theory based on the Strutinsky method. Our results confirm the spin value of 0 for 21·4 h isomer in154Tb and they establish the spin value of 3 for the 2277·0 and 2336·1 keV levels and the spin value of 4 for the 2416·3 keV level in154Gd.

On the magnetic dipole moment of the153Tb ground state

Temperature dependence of the angular distribution anisotropy of the 212·0 keV gamma-ray following the decay of153Tb oriented in a gadolinium host was measured at temperatures from 16 to 70 mK. Magnetic dipole hyperfine splitting parameter a0 for153Tb(Gd) and magnetic dipole moment of the153Tb ground state were estimated to be ¦a0¦≧1·2×10−5 eV and ¦μ¦≧≧3·1 nuclear magnetons, respectively.

Nuclear orientation study of155Tb decay

The angular distribution of gamma-rays following the electron capture decay of155Tb nuclei oriented in a gadolinium host has been studied at temperatures between 16 and 80 mK. The magnetic dipole hyperfine splitting parameter for155Tb(Gd) has been deduced and the value of the magnetic dipole moment of155Tb ground state has been found to beμ=2.0(2)μN. The multipole mixing ratios have been determined for 9 gamma-transitions in155Gd.

NMR on oriented54Mn in nickel

The NMR/ON of thin foil polycrystalline54MnNi was measured at 16 mK. From zero field resonance frequencyv00=273·1 (1) MHz the hyperfine fieldBhf=−32·55 (6) T was deduced, the slope beingdv/dB=0·935 MHz/T.