The spectroscopy of sup 164 Yb and the loss of collectivity at high spins in even-even ytterbium isotopes

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:7205964

Xie, Hong

High spin states in {sup 164}Yb were populated via {sup 124}Sn({sup 44}Ca,4n){sup 164}Yb reaction at the 25 MV Tandem Accelerator at the Holifield Heavy Ion Research Facility. Three new transitions were added to the previously known decay sequences of {sup 164}Yb. The extracted B(E1, I {yields} I {minus} 1)/B(E2, I {yields} I {minus}2) ratios for {sup 164}Yb show an enhancement compared to its neighboring isotopes, which suggests that {sup 164}Yb neutron number N = 94 possess an instability with respect to the octupole degree of freedom. Lifetimes of high spin states with I{sup {pi}} = 20{sup +} to 32{sup +} in the yrast band and 23{sup {minus}} to 25{sup {minus}} in the ({minus},1)-band in {sup 164}Yb were measured by using the Doppler shift attenuation method. A reduction of the stretched E2 transition quadrupole moments was observed at high spins in the yrast decay sequences. A systematic summary of the available experimental lifetime data and kinetic moments of inertia has been given for even-even ytterbium isotopes. The loss of collectivity implies that at high rotational frequency, nuclei undergo shape changes (mainly toward a reduced {beta}{sub 2} deformation for well deformed ytterbium isotopes), which can be understood as arising from the deoccupation of strongly shape-polarizing, high-j, anti aligned orbits with nucleons moving opposite to the rotation axis. The self-consistent cranking calculations, the so-called total routhian surface calculations, were performed for several ytterbium isotopes. Qualitatively the drops observed in transition quadrupole moments at high spin states in the yrast band are reproduced when the reduction of the pair correlation with increasing rotational frequency is taken into account.

• Research Organization: Vanderbilt Univ., Nashville, TN (United States)
• OSTI ID: 7205964
• Country of Publication: United States
• Language: English

Related Subjects

663220* -- Electromagnetic Transitions-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CALCIUM 44 REACTIONS
CHARGED-PARTICLE REACTIONS
CRANKING MODEL
DATA
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
HEAVY ION REACTIONS
INFORMATION
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LIFETIME
MATHEMATICAL MODELS
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEI
QUADRUPOLE MOMENTS
RADIOISOTOPES
RARE EARTH ISOTOPES
RARE EARTH NUCLEI
SECONDS LIVING RADIOISOTOPES
SHAPE
STABLE ISOTOPES
TARGETS
TIN 124 TARGET
YRAST STATES
YTTERBIUM 176
YTTERBIUM ISOTOPES