Semi-classical and anharmonic quantum models of nuclear wobbling motion

A semi-classical model for wobbling motion is presented as an extension to the Bohr-Mottelson model of wobbling motion. Using the resultant wobbling potential, a quantum mechanical equation is derived for anharmonic wobbling motion. We then attempt to explain the anharmonicity observed in the excited bands of two wobbling phonons in the A=160 region.Comment: 5 pages, 2 figures, accepted in Phys. Lett.

Evidence for particle-hole excitations in the triaxial strongly-deformed well of ^{163}Tm

Two interacting, strongly-deformed triaxial (TSD) bands have been identified in the Z = 69 nucleus ^{163}Tm. This is the first time that interacting TSD bands have been observed in an element other than the Z = 71 Lu nuclei, where wobbling bands have been previously identified. The observed TSD bands in ^{163}Tm appear to be associated with particle-hole excitations, rather than wobbling. Tilted-Axis Cranking (TAC) calculations reproduce all experimental observables of these bands reasonably well and also provide an explanation for the presence of wobbling bands in the Lu nuclei, and their absence in the Tm isotopes.Comment: 13 pages, 7 figure

gg-factor and static quadrupole moment for the wobbling mode in 133^{133}La

The $g$-factor and static quadrupole moment for the wobbling mode in the nuclide $^{133}$La are investigated as functions of the spin $I$by employing the particle rotor model. The model can reproduce the available experimental data of $g$-factor and static quadrupole moment. The properties of the $g$-factor and static quadrupole moment as functions of $I$ are interpreted by analyzing the angular momentum geometry of the collective rotor, proton-particle, and total nuclear system. It is demonstrated that the experimental value of the $g$-factor at the bandhead of the yrast band leads to the conclusion that the rotor angular momentum is $R\simeq 2$. Furthermore, the variation of the $g$-factor with the spin $I$ yields the information that the angular momenta of the proton-particle and total nuclear system are oriented parallel to each other. The negative values of the static quadrupole moment over the entire spin region are caused by an alignment of the total angular momentum mainly along the short axis. Static quadrupole moment differences between the wobbling and yrast band originate from a wobbling excitation with respect to the short axis.Comment: 6 pages, 4 figure

Lifetimes of triaxial superdeformed states in \chem{^{163}Lu} and \chem{^{164}Lu}

Lifetimes of states in the yrast superdeformed bands of $^{163}$Lu and $^{164}$Lu were determined in a Doppler-shift attenuation-method experiment. From fractional Doppler shifts and line shapes, average transition quadrupole moments, $Q_{\rm t} = 8.2_{-0.6}^{+1.0}$ b and $7.1_{-0.6}^{+0.5}$ b, were deduced for one of the bands in $^{163}$Lu and $^{164}$Lu, respectively. These values are much larger than the quadrupole moment of the normal-deformed yrast band in $^{163}$Yb, $Q_{\rm t} = 4.9_{-0.4}^{+1.3}$ b, that was also determined in this experiment. Comparison to cranking calculations indicates that both superdeformed bands correspond to a local potential energy minimum with a pronounced triaxiality, $\gamma\sim 20^\circ$

Comparative quadrupole moments of triaxial superdeformed states in \chem{^{163,164,165}Lu}

Average transition quadrupole moments in the yrast triaxial superdeformed bands of $^{163}$Lu, $^{164}$Lu and $^{165}$Lu were determined in a Doppler-shift attenuation-method experiment. Fractional Doppler shifts were determined in $\gamma$-ray coincidence spectra measured with the Gammasphere array. The transition quadrupole moments derived from these data show a decrease from $^{163}$Lu to $^{165}$Lu which is not predicted by total-energy surface calculations

First evidence for triaxial superdeformation in \chem{^{161}Lu} and \chem{^{162}Lu}

High-spin states in $^{161}$Lu and $^{162}$Lu have been investigated using the GASP $\gamma$-ray spectrometer array. Excited states in these nuclei have been populated through the $^{100}$Mo($^{65}$Cu, $x$n) reaction at a beam energy of 260 MeV. Four presumably triaxial superdeformed bands, three in $^{162}$Lu and one in $^{161}$Lu, have been observed. This is the first evidence for triaxial superdeformation in the two isotopes