The study of scissors mode excitations in [sup 162,164]Dy by inelastic neutron scattering

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7103889

Johnson, E L

Low-energy collective excitations in nuclei arising from the explicit inclusion of separate proton and neutron degrees of freedom have been predicted within the framework of various nuclear models. In well-deformed even-even nuclei, those isovector excitations appear at excitation energies near 3 MeV, have spin and parity J[sup [pi]] = 1[sup +], and exhibit a B(M1) strength of [approximately]2-3 [mu][sub N][sup 2]. The geometrical intepretation of the excitation as an out-of-phase angular oscillation of the protons versus the neutrons has naturally led to the designation scissors mode' for these states. Scissors mode states have been experimentally observed in deformed nuclei ranging from [sup 46]Ti to [sup 238]U, and theoretical treatments have included various collective models as well as a variety of microscopic descriptions. In previous studies, a considerable amount of data has been collected on nuclei in the rare earth region, primarily from electron scattering and photon scattering measurements. A particularly interesting case is [sup 164]Dy, since this nucleus shows substantially more fragmentation and a much larger total B(M1) strength that that seen in similar nuclei. Inelastic neutron scattering (INS) studies were initiated on the nuclei [sup 162]Dy and [sup 164]Dy to determine B(M1)'s directly from lifetimes obtained utilizing the Doppler Shift Attenuation Method, to identify possible branchings to lower-lying states, and to locate possible rotational excitations built on scissors mode states. In a state-to-state comparison of B(M1)'s with the results of photon scattering measurements, the INS values are in general agreement with previous determinations. The agreement for [sup 162]Dy is quite good, but a serious discrepancy exists for the three states near 3.1 MeV in [sup 164]Dy where the INS estimates are lower than the photon scattering strengths by nearly a factor of three.

• Research Organization: Kentucky Univ., Lexington, KY (United States)
• OSTI ID: 7103889
• Country of Publication: United States
• Language: English

Related Subjects

663110* -- General & Average Properties of Nuclei & Nuclear Energy Levels-- (1992-)
663570 -- Nuclear Mass Ranges-- A=150-189-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CHEMICAL ANALYSIS
COLLECTIVE EXCITATIONS
DYSPROSIUM 162
DYSPROSIUM 164
DYSPROSIUM ISOTOPES
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
EXCITATION
INTERMEDIATE MASS NUCLEI
ISOTOPES
NONDESTRUCTIVE ANALYSIS
NUCLEI
RADIATION SCATTERING ANALYSIS
RARE EARTH ISOTOPES
RARE EARTH NUCLEI
STABLE ISOTOPES