[en] The report contains the notes from a series of lectures on the Interacting Boson Approximation (IBA) model. The lectures were presented at Lawrence Livermore National Laboratory on July 28, 30 and August 1, 1982 by Jolie A. Cizewski from Yale University. The IBA was developed by F. Iachello and A. Arima starting about seven years ago to understand collective quadrupole excitations in medium and heavy mass nuclei away from closed shells. Since then the formalism has been extended to odd-mass nuclei and considerable work has gone into understanding the microscopic construction of the bosons in this model. The IBA has been applied to nuclei as light as Zn and Ge and as heavy as U and Pu; to nuclei near closed shells, such as Mo and Hg; to stable nuclei and nuclei far from stability. The present lectures were designed to give the experimentalist an introduction to the IBA and to give specific examples of how it could be applied to understand the structure of heavy even and odd mass nuclei. Much of the emphasis was on the symmetries (and supersymmetries) of the model and how the use of symmetries enabled the relatively straightforward understanding of empirical systems as deviations from these symmetries. The richness of possible applications of the IBA to understanding collective phenomena in nuclei was not fully explored, but rather a few illustrative examples were selected and described in detail. The references, accumulated at the end of this report, provide a more comprehensive, although not complete, list of tests of the IBA in even mass nuclei and the new symmetries in odd mass nuclei. The references also list the main theoretical papers which provide the details of the IBA formalism

[en] The low spin level structure of ¹⁹⁶Pt was extensively investigated with the (n,γ) reaction. Low energy and high energy measurements of γ-ray transitions following thermal and resonance capture were performed. High energy transitions following 2-keV capture were measured. These average capture data were of sufficient sensitivity to guarantee the identification of all 0⁺, 1⁺ and 2⁺ states in ¹⁹⁶Pt below 2.5 MeV excitation energy. These results concerning the γ transitions and level energies in ¹⁹⁶Pt were combined with the extremely high resolution low energy γ-ray measurements from the bent-crystal spectrometers at the Institut Laue--Langevin and information from earlier investigations to generate an exhaustive level scheme which encompasses approximately 60 levels and 200 transitions. The structure of the low spin positive-parity states as observed were compared to a number of existing nuclear models in this mass region. It was found that the Interacting Boson Approximation (IBA) model of Iachello and Arima provides a description of the positive-parity collective excitations which is in excellent agreement with the observed level structure. In fact, ¹⁹⁶Pt is the first empirical candidate for the O(6) symmetry of the IBA. Given the identification of ¹⁹⁶Pt as exhibiting the O(6) symmetry, the systematics of the other Pt and Os nuclei were examined from a new viewpoint. It was found that these nuclei can be understood in terms of successive departures from the O(6) limit as introduced by the quadrupole--quadrupole interaction of the IBA. The predictions of this perturbed O(6) scheme reproduce the measured relative B(E2) values for the 0⁺ states, γ bands and K = 4 bands and the absolute B(E2) values in the Pt--Os nuclei

[en] The (t,p) and (t/sup →/,α) reactions on enriched ¹⁹¹¹⁹³Ir targets were investigated. The resultant spectroscopic strengths are compared and contrasted with the expectations of the dynamical supersymmetry scheme proposed for the Pt-Ir region. 1 figure, 2 tables

[en] Two-neutron transfer studies in Pt and Os were investigated. The extracted relative enhancement factors in Pt were found to be in excellent agreement with the 0(6) limit predictions. The differences in transfer strength between Pt and Os (t,p) could not be reproduced within the present framework of the Interacting Boson Approximation Model. 3 figures

[en] The Stewardship Science Academic Alliances (SSAA) were inaugurated in 2002 by the National Nuclear Security Administration of the U. S. Department of Energy. The purpose is to enhance connections between NNSA laboratories and the activities of university scientists and their students in research areas important to NNSA, including low-energy nuclear science. This paper highlights some of the ways that the SSAA fosters education and training of graduate students and postdoctoral scholars in low-energy nuclear science, preparing them for careers in fundamental and applied research and development

[en] It is shown that the systematics of the fragmentation of Nilsson strength in the Hf--Os region can be understood in terms of varying quadrupole and hexadecapole deformations. 2 figures

[en] It is shown that the energy gap in nonspherical even--even nuclei is rather sharply delineated in γ-ray spectra following average resonance neutron capture. The relation to other methods of determining the energy gap is also presented

[en] Odd-odd nuclei are very complicated systems because many coupling schemes are possible between the various quasi-particle configurations. By studying these nuclei one can test different coupling schemes and their effects on the nuclear structure, e.g., the blocking effect. The previously unknown odd-odd nucleus ¹⁷⁸Ir has been studied via the reactions ¹⁵⁶Gd(²⁷Al,5n) and ¹⁵²Sm(³¹P,5n). The measurements were performed at the Holifield Heavy Ion Research Facility using the Spin Spectrometer and the Compact Ge array. The excitation functions and the multiplicity K distributions of γ rays were used to identify transitions belonging to this nucleus. The preliminary study leads to assignment of several rotational bands in ¹⁷⁸Ir, among them a doubly-decoupled band that resembles those in heavier Ir isotopes. The nature of this band and other band assignments, based on signature splitting and B(M1)/B(E2) ratios, will be discussed

[en] A previous experiment at Early Implementation GAMMASPHERE using the ¹⁷⁴Yb(²⁹Si,5n)²⁹₁₉₈₈₄Po reaction revealed a candidate for a superdeformed (SD) band. A follow-up experiment at GAMMASPHERE with the same reaction has been performed and the results will be discussed. A large number of SD and Ml rotational bands have been discovered in recent years in nuclei near Z∼79-83 and N∼110-116, including Bi (Z=83) nuclei. Calculations by Bonche, et al., and Satula, et al., predict second minima for prolate deformation with Β 0.5 for the polonium nuclei

[en] The particle-core coupling model (PCM) has been used to describe a number of nuclei in terms of a vibrational core coupled to one or two extra nucleons. Most recently, it has been applied to N = 84 isotones with reasonable agreement between experiment and theory. The authors have attempted to interpret their extensive data on A = 118-126 Te isotopes in terms of purely vibrational structures, with at best limited success. As a continuation of this work, they are currently investigating the low-lying structure of the even-even Te isotopes in terms of the PCM. For each isotope, parameters describing the quadrupole phonon core, and the nucleon-phonon and nucleon-nucleon interactions are fixed from a fit to the low lying energy levels in that nucleus. The transition probabilities and remaining energy levels predicted by the model are then compared to their experimental values