Nuclear collective quadrupole-octupole excitations in the U(16) spdf interacting boson model

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7142345

Kusnezov, D F

The algebraic description of nuclei in which quadrupole and octupole collective degrees of freedom are simultaneously present is studied within the framework of the U(16) spdf interacting boson model. These degrees of freedom seem to be important in the collective structure of the rare-earth and actinide nuclei. In Part I, we introduce and discuss the algebraic structure of the U(16) spdf interacting boson model. Dynamical symmetry breaking schemes are explicitly constructed, primarily using a simple ansatz. The generators, commutation relations, Killing forms, linear and quadratic Casimir operators and the expectation values of the Casimir operators are all listed for each subalgebra. In Part II, we study some related non-dynamical symmetry phenomenology in nuclei. In particular we apply some of the algebraic results of Part I to explain the suggested experimental appearance of octupole deformation in the even-even rare-earth nuclei near {sup 146}Ba. We show that the U(13) sdf model does not provide any reasonable explanation of the experimental E1 transition data, even with the introduction of strong ground state octupole deformation. We then present a simple description of the energy and electromagnetic transition data within the framework of the U(16) spdf model, utilizing a mass dependent E1 operator, and show that even 1-pf boson provides a reasonable description of all the data. We next study the energies and electromagnetic transitions of collective positive and negative parity states in the even-even {sub 56}Ba, {sub 58}Ce, {sub 60}Nd and {sub 62}Sm isotopes, with 82 < N < 94, using a U(16) hamiltonian that describes the transition from a vibrational structure (U(7) {times} U(5) {times} U(3) {times} U(1)) to rotational structure (SU(3) {times} SU(3)).

• Research Organization: Princeton Univ., NJ (USA)
• OSTI ID: 7142345
• Country of Publication: United States
• Language: English

Related Subjects

651000* -- Nuclear Physics
653001 -- Nuclear Theory-- Nuclear Structure
Moments
Spin
&amp; Models
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALKALINE EARTH ISOTOPES
BARIUM 146
BARIUM ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCULATION METHODS
COLLECTIVE EXCITATIONS
COMPUTER CODES
DATA ANALYSIS
E1-TRANSITIONS
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
EXCITATION
INTERACTING BOSON MODEL
INTERMEDIATE MASS NUCLEI
ISOTOPES
MATHEMATICAL MODELS
MULTIPOLE TRANSITIONS
NUCLEAR MODELS
NUCLEI
RADIOISOTOPES
SECONDS LIVING RADIOISOTOPES
SHELL MODELS
SYMMETRY