[en] The research activities of the experimental nuclear structure group at Vanderbilt University carried out under Contract AS05-76ER05034 with the Department of Energy for the period September 1986 to July 1987 are reported here. Research continues in the areas of (1) in-beam γ-ray spectroscopy including cooperations with scientists at Oak Ridge, Univ. of Rochester, Univ. of Koeln, Louisiana State Univ., Univ. of Florida, Idaho Falls, and Univ. of Notre Dame; (2) studies of nuclei far from stability at UNISOR and at the recoil mass spectrometer at the University of Rochester; (3) nucleon transfer reaction and fusion-fission studies with scientists at ORNL, Argonne National Laboratory, Univ. of Michigan, and University of Kansas; (4) theoretical studies with scientists at Univ. Frankfurt, Univ. Tuebingen, Univ. Lund, Brookhaven, Lawrence Berkeley, and ORNL; (5) other studies. In general, abstracts of papers published or submitted for publication in this period make up this report along with brief reports of work in process and complete copies of a few conference papers

[en] Progress summaries are given in the fields of in-beam gamma ray spectroscopy, nuclei far from stability, nuclear reaction mechanism studies, delta-electron spectroscopy, theoretical studies, and other research and activities. Status of the Joint Institute for Heavy Ion Research is reviewed

[en] Problem linked with nuclei operation orientation (NOC) is discussed

[en] Discoveries of many different types of nuclear shape coexistence are being found at both low and high excitation energies throughout the periodic table, as documented in recent reviews. Many new types of shape coexistence have been observed at low excitation energies, for examples bands on more than four different overlapping and coexisting shapes are observed in ¹⁸⁵Au, and competing triaxial and prolate shapes in ⁷¹Se and ¹⁷⁶Pt. Discrete states in super-deformed bands with deformations β ₂ ∼ 0.4-0.6, coexisting with other shapes, have been seen to high spin up to 60ℎ in ¹⁵²Dy, ¹³²Ce and ¹³⁵Nd. Super-deformed nuclei with N and Z both around 38 and around Z = 38, N ≥ 60. These data led to the discovery of new shell gaps and magic numbers of 38 for N and Z and 60 for N but now for deformed shapes. Marked differences in structure are observed at spins of 6 to 20 in nuclei in this region, which differ by only two protons; for example, ⁶⁸Ge and ⁷⁰Se. The differences are thought to be related to the competing shell gaps in these nuclei

[en] The research activities of the experimental nuclear structure group at Vanderbilt for the period August 1982 to August 1983 are reported. Research continues in the areas of, (a) in-beam γ-ray spectroscopy including cooperations with scientists at Oak Ridge, University of Koeln, Max Planck Inst./Heidelberg, GSI/Darmstadt, University of Florida and Florida State University; (b) studies of nuclei far from stability at UNISOR and at the on-line He refrigerator at the Leuven on-line separator; (c) pre-equilibrium (massive transfer) emission processes in fusion reactions at ORNL; (d) nucleon transfer reaction studies with scientists at ORNL, Los Alamos and Brookhaven; (e) electron scattering on ¹⁸⁰Hf at MIT Bates Laboratory; (f) delta-electron spectroscopy at the Max Planck Institute in Heidelberg; (g) theoretical studies with scientists at University of Frankfurt, Brookhaven, Lawrence Berkeley and ORNL; and (h) other studies

[en] An overview of many of the new insights extracted from γ,γ and γ-γ-γ coincidence studies of spontaneous fission of ²⁵²Cf and ²⁴²Up with large detector arrays at ORNL and Gammasphere will be presented. These include direct measurements of yields and neutron multiplicities from 0 to l0v for five correlated pairs, identification of a number of cold fission (cluster radioactivity) channels, identification of new structures and behaviors in many neutron-rich nuclei from ⁹⁴Sr to ¹⁶⁰Sm. From the yields of the correlated pairs, a new, second mode of SF is observed in the Mo-Ba pairs with much lower total kinetic energy. This mode goes via a hyperdeformed shape (3:1 axis ratio) for ¹⁴⁴Ba, ¹⁴⁵Ba, or ¹⁴⁶Ba. Calculations indicate a third minima in ²⁵²Cf at Β₃ ∼ 0.7 and Β₂ ∼ 0.9. The zero neutron cluster radioactivity yields for odd-odd Mo-Ba pairs are about four times larger than for the even-even ones in agreement with recent cluster radioactivity predictions. Identical bands are observed in ^98,100Sr, ^108,110Ru, ^144,146Ba, and ^152,154Nd nuclei and new types of identical bands in ^156,158,160Sm nuclei, and the first identical octupole bands. Octupole deformation is seen in N = 86, ¹⁴²Ba, ¹⁴⁴Ce and the new high spin octupole states to 19^- exhibit the first backbending and quenching of the static octupole strength as predicted by theory. Selected examples of the new physics being seen will be presented

[en] New generations of 4π gamma-ray detectors, recoil mass spectrometers (RMS), and radioactive beam accelerators will open up many new areas of research, including present inaccessible in-beam and radioactive decay studies of exotic nuclei still farther off stability. The new generation RMS and radioactive beam developments at the Holifield Heavy Ion Research Facility are presented. Current research and further prospects to probe the N -- Z line up to ¹⁰⁰Sn are described. Superdeformation in A -- 70 to 190 nuclei is described in terms of its underlying physics of reinforcing proton and neutron shell gaps which lead to new superdeformed, doubly-magic nuclei. Recent results provide new insights into the coexistence of multiple nuclear shapes near the ground states

[en] Studies of the properties of exotic nuclei have revealed a surprising richness and diversity in their shapes, structures, and decay modes far exceeding our understandings and expectations of even a decay ago. From studies of far-off-stability exotic nuclei have come evidence for the coexistence of different nuclear shapes in the same nucleus, new regions of unusually large deformation, new ground-state phase transitions from one shape to another, new magic numbers but now for deformed shapes, and for the importance of reinforcing shell gaps. New exotic decay modes include a wide variety of beta delayed particle emission and heavy cluster emissions such as ¹⁴C and ²⁴Ne. The new deformed magic numbers of 38 and 60 seen far off stability clearly support that there are likely other ''magic'' numbers for protons and neutrons which give stability to different deformed shapes. Perhaps these other new magic shell gap numbers at large deformation could influence the sticking of two very heavy nuclei in collisions such as U on Cm. Finally, another area which could have a bearing on the formation, motions, and structures of giant nuclear systems involves the recent observation of very energetic, light particle (proton, alpha) emission with up to 50% and more of the total incoming energy in a collision, for example in 300 MeV ³²S on Ta. 43 refs., 11 figs., 2 tabs

[en] Studies of in-beam gamma rays from heavy-ion induced reactions were used to extensively explore the higher spin states of some of the even-mass nuclei around mass 70. This not only allowed observation of higher members of the ground-state band (up to spins of to 16), but also revealed a surprising variety of other bands. The various bands in such nuclei are reviewed, and some possible theoretical explanations are discussed. Five types of bands are considered. 32 references

[en] Results from various groups which use on-line low temperature nuclear orientation techniques are presented. Several nuclear parameters have been successfully studied: rotational levels, nuclear deformation, and decay modes. Future prospects include multiparameter analysis, relaxation and pre-orientation, new separators, and alpha decay studies. 33 refs., 5 figs