C. Gehringer

γ rays in the 2–18 MeV range from the reaction 120Sn(28Si, 4n)144Gd

Abstract Unresolved γ radiation preceding the decay of the I π = 10 + isomer in 144 Gd has been studied via the 120 Sn + 28 Si reaction using a large NaI detector. The γ-ray multiplicity and anisotropy have been measured for 2 ⩽E⩽ 18MeV . At energies above 8 MeV a broad shoulder, presumably arising from the giant dipole resonance, is observed on top of the statistical tail. These high-energy γ rays are shown to deexcite high spin states and have a nearly isotropic angular distribution.

A comparative study of superdeformation in 146,147,148Gd. Possible manifestations of the pseudo-SU3 symmetry, octupole shape susceptibility and superdeformed deep-hole excitations

Abstract Two discrete superdeformed (SD) bands have been identified in the nucleus 147Gd and the twin-band mechanism studied by comparison with SD results for 146,148Gd. Theoretical interpretation in terms of nucleonic orbitals with the Woods-Saxon potential is consistent with the pseudo-spin symmetry picture and the octupole susceptibility mechanism predicted by theory.

Second backbending in the yrast line of 156Er

Abstract High spin yrast states of 156 Er were investigated using the reactions 141 Pr( 19 F,4nγ) and 123 Sb( 37 Cl, 4nγ), the latter in connection with a sum-crystal. In addition to the backbending at I = 12 h , a second one is found at I = 26 h ; and the yrast band is extended up to I = 32 h ; . These results are interpreted in terms of a Hartree-Fock-Bogolyubov Cranking (HFBC) method. It is demonstrated that for deformations in the vicinity of the Strutinsky equilibrium deformation, both a 2qp proton band crossing the yrast band or a 4qp neutron band crossing the yrast band can cause strong secondary backbending.

Magnetic moments of the Iπ = 10+ isomers in Ce and Nd N = 80 isotones

Abstract Nuclear g -factors have been measured for the I π = 10 + isomers in 138 Ce and 140 Nd by the pulsed-beam time-differential spin-rotation method. The 3538 keV level in 138 Ce and 3621 keV level in 140 Nd were excited by the 130 Te( 12 C, 4nγ) and 128 Te( 16 O, 4nγ) reactions, respectively. The nuclear g -factors of these 10 + states were measured to be g = −0.176(10) and g = −0.192(12) for 138 Ce and 140 Nd respectively. These values are well explained by a two neutron-hole h 11 2 −2 configuration for these states.

Feeding of the superdeformed yrast band in 149Gd

Abstract The feeding pattern of the superdeformed yrast band in 149 Gd has been found to remain essentially the same, using the 124 Sn+ 30 Si reaction at beam energies of 150, 155 and 160 MeV leading to different input angular momenta and excitation energies in the compound nuclear system. This similarity as well as the relative yields of the superdeformed states as a function of beam energy may be understood in terms of the nuclear level density dependence on deformation and the onset of fission. In addition, it has been shown that, at all three beam energies, the selection of high-energy gamma rays does not enhance the yield of the superdeformed yrast states.

Multipolarity of the continuum γ-rays in 152Dy and 160Er via linear polarisation measurements

Abstract The multipolarity of the continuum transitions in 152 Dy and 160 Er has been deduced from γ-ray linear polarisation and angular distribution measurements. The yrast part for 160 Er agrees with the predicted stretched E2 cascade. The statistical parts for both 152 Dy and 160 Er consist of a mixture of dipolar stretched and non-stretched transitions, predominantly of electrical character. Below 1.5 MeV, the data of 152 Dy exhibit a different structure, and reveal a stretched M1 component in the low-energy region.

Magnetic moment of the 2543 keV 7+ state in 40K

Abstract The nuclear g-factor of the 2543 keV, 7+ state 40K has been measured as g = 0.59 ± 0.10. Time-integral perturbed angular distributions were measured in an external magnetic field and, after implantation, in the hyperfine field at potassium in nickel. The experimental value is discussed within the f 7 2 2 and d 3 2 −2 f 7 2 2 , configurations.

Vies moyennes des niveaux a 53.2 keV et 111.5 keV et moment magnétique du niveau a 111.5 keV du 58Co

Abstract To study the lowest levels of 58 Co, nγ angular correlations (method II) and g -factor and lifetime measurements have been performed using the 58 Fe(p, nγ). 58 Co reaction. The lifetime of the 111.5 keV level was found to be T 1 2 = 0.18±0.03 ns . The lifetime of the 53.2 keV level was remeasured and found to be T 1 2 = 10.4±0.3 μ s . The g -factor of 111.5 keV state was determined to be g = +0.74±0.13 using the IPAD method. Branching and mixing ratios have also been obtained. Values of J π = 4 + and 3 + were assigned to the levels at 53.2 keV and 111.5 keV, respectively.

The unusual strenght of the 5.14 → 1.27 MeV, 2− → 2+, transition in 22Ne

Abstract The lifetime of the 5.14 MeV excited state of 22 Ne was investigated by use of the electronic timing, recoil distance and Doppler shift attenuation techniques. A mean life τ = 1.2±0.3 ps was obtained, corresponding to a transition strenght of 9.8 × 10 −6 W.u. for the El decay of this state.

Lifetime of the second excited state of 43K

Abstract The lifetime of the 738 keV level of 43K, excited by means of the 40Ar(α, p)43K reaction, has been deduced from the distribution of time delays between protons and decay γ-rays. The half-life, 205±10 ns, favors a J π = 7 2 − assignment.