H. Haas

E2 moments andg-factors in neutron deficient lead isotopes

The half-lives of the (vi13/2)2Iπ=12+ isomers in190, 192pb were measured asT1/2 =7.9(4) μs and 1.10(5) μs, respectively. The quadrupole moment and theg-factor of the corresponding state in194Pb were determined toQ=49(3) efm2 andg=−0.167(2) using the perturbed angular distribution method. Additionalg-factor and lifetime information was obtained for a number of isomers in194, 195, 196, 197, 198, 199, 200Pb also involvingi13/2 neutrons. The results are discussed in comparison to a two-quasiparticle Tamm-Dancoff calculation in the full shell using the surface delta interaction.

Magnetic moments of (νi132)−n isomers in neutron-deficient lead isotopes

Abstract The magnetic moments of the 12+ isomers in 192, 196, 198, 200, 206Pb and of the 33 2 + isomer in 205Pb have been measured using the PAD technique. The results for the g-factors are: g(192) = −0.173(2), g(196) = −0.1600(15), g(198) = −0.1552(15), g(200) = −0.1512(15), g(206) = −0.1496(18), and g(205) = −0.148(5). As all states have a rather pure (νi 13 2 ) −n configuration, the values reflect directly the νi 13 2 orbital. They show a decrease towards the more neutron-deficient isotopes attributed to the reduced core polarisation as a result of decreasing occupation of the i 13 2 neutron shell. The measured systematics are discussed regarding core polarisation, mesonic corrections, and small admixtures of core-excited states to the i 13 2 wave function.

Quadrupole moments of high-spin isomers in astatine isotopes

Abstract The quadrupole moments of the isomeric π( h 9 2 ) 2 i 13 2 and π( h 9 2 ) 3 states in 209,210,211 At show a large increase with the removal of neutrons from the closed N=126 shell. The increase is discussed in terms of an enhanced polarization of the broken core by the aligned valence protons in high-spin orbitals.

A 2π neutron multiplicity filter for in-beam γ-ray spectroscopy of neutron deficient nuclei

Abstract A 2π neutron multiplicity filter consisting of 16 detectors filled with NE213 liquid scintillator has been designed and assembled for in-beam γ-ray spectroscopy of neutron deficient nuclei. Results are presented for the efficiency for single and multiple events, detector cross talk by scattering and n-γ discrimination, both, for a 252Cf source and a typical (hi, xn yp zα) reaction.

Magnetic moments of isomeric states in146Gd

The observation of 146Gd showing features of a double magic nucleus (i) has focussed interest on the shell model structure of this nucleus and its neighbours. In contrast to all other doubly closed shell nuclei, there exist several isomeric states in ]46Gd, suitable for a measurement of the nuclear magnetic dipole moments by time-differential observation of the spin precession in an external magnetic field. This promises a distinction between several possible shell model configurations.

Magnetic moment and half-life of the isomeric 112− state in 107Cd

Abstract An isomeric level in 107Cd at 845 keV populated by the reactions 107Ag(p, n), 106Cd(d, p) and 104Pd(α, n) has been observed. The half-life of this state is T 1 2 = 77(7) ns , and the spin and parity are I π = 11 2 − . The magnetic moment has been determined by the pulsed beam time-differential perturbed angular distribution method (DPAD) to be μ = −1.012(12) n.m.

g-Factors of high spin isomers in 202Bi, 203Bi and 205Bi

Abstract The g-factors of the 10− and 17+ isomers in 202Bi and of the 21 2 + and 25 2 + isomers in 203Bi and 205Bi were measured using the in beam TDPAD method. The results g(10−, 202Bi) = 0.255 (3), g17+; 202Bi = 0.121 (3), gav( 21 2 + , 25 2 + ; 203Bi) = 0.266 (4) and gav( 21 2 + , 25 2 + ; 205Bi) = 0.257 (4) are compared to calculated values for the shell-model configurations suggested for the isomeric states.

Recoil distance lifetime measurements in 125Xe

Lifetimes of excited states in 125Xe populated in the (12C, 3n) reaction on 116Cd were measured by the recoil distance method. A delayed tagging technique was employed to preferentially detect the non-yrast transitions in the νg72 band system built on the Iπ = 72+, T12 = 140 ns isomer in 125Xe. The following mean lifetimes τ(I)π, Ex) were obtained: 115 ± 25ps (92+, 597 keV), 11.3 ± 1.1 ps (112+, 871 keV), 4.2 ± 1.5ps (132+, 1210 keV), 3.8 ± 1.3ps (152+, 15360 keV); 12.5 ± 1.3 ps (152−, 797 keV). The results are well described within the triaxial-rotor-plus-particle model.

Magnetic moments of the anomalous parity 52+ 13.3 keV state of 73Ge

The g-factor of the 3 μs 52+ level in 73Ge was determined to be g=−0.0376±0.0010 by the time-differential perturbed angular correlation method. The magnetic moment of the anomalous parity state is discussed on the basis of the extended quasiparticle-phonon coupling model.

Magnetic hyperfine field for arsenic in nickel

The magnetic hyperfine field for As in nickel has been remeasured by DPAD techniques. Using a sandwich type of target the excited As nuclei were recoil-implanted into unpolarized nickel layers after the reaction71Ga (α, n)74As. The resultHhf (300 K)=106 (2) kOe differs considerably from a former IPAC measurement.