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Study of {sup 189}Bi{sup m} {alpha} decay

Description: In a series of {sup 48}Ti bombardments of {sup 144}Sm the decay energy of the {sup 189}Bi{sup m} ({pi}s{sub 1/2}) {alpha} transition that proceeds to the {pi}s{sub 1/2} ground state of {sup 185}Tl was measured to be 7.30(4) MeV. This result establishes the excitation energy of {sup 189}Bi{sup m} as 190(40) keV rather than the adopted 92(10)-keV value. Our data thus indicate a leveling off in excitation energy at N {approx} 106 for the s{sub 1/2} intruder state in odd-A Bi isotopes.
Date: December 1995
Creator: Batchelder, J. C.; Zganjar, E. F. & Toth, K. S.
Partner: UNT Libraries Government Documents Department

Entrance channel dependent light-charged particle emission of the {sup 156}Er compound

Description: Light-charged particle decay from the {sup 156}Er compound nucleus, populated by {sup 12}C+{sup 144}Sm and {sup 60}Ni+{sup 96}Zr at the same excitation energy, were measured in coincidence with the evaporation residues. The high energy slope of charged particle spectra for the {sup 60}Ni-induced reaction is steeper than for the {sup 12}C-induced reaction. Model calculations including particle evaporation during compound nucleus formation result in good agreement with the data. This suggests that the difference in the charged particle spectra between the two entrance channels is due to a longer formation time in the {sup 60}Ni-induced reaction. 14 refs., 3 figs.
Date: September 1, 1996
Creator: Liang, J.F.; Bierman, J.D.; Kelly, M.P.; Sonzogni, A.A.; Vandenbosch, R. & van Schagen, J.P.S.
Partner: UNT Libraries Government Documents Department

Suppression of neutron emission in heavy ion induced fusion reactions: entrance channel effect and/or superdeformed shapes

Description: In the 233-MeV /sup 64/Ni + /sup 92/Zr reaction the emission of two neutrons constitutes the strongest decay channel, in contrast to statistical model calculations which predict the emission of three neutrons to be the strongest by more than one order of magnitude. Possible explanations for the apparent neutron suppression in terms of unusually large gamma-decay width, anomalously energetic neutrons or an unknown yrast line have been ruled out. Here we report on a series of experiments aimed at a better understanding of this suppression. The neutron multiplicity M/sub n/ has been obtained for the 55 to 75 MeV /sup 12/C + /sup 144/Sm and the 225 to 290 MeV /sup 64/Ni + /sup 92/Zr reactions leading to the same compound nucleus /sup 156/Er.
Date: January 1, 1985
Creator: Janssens, R.V.F.; Holzmann, R.; Henning, W.; Khoo, T.L.; Lesko, K.T.; Radford, D.C. et al.
Partner: UNT Libraries Government Documents Department

Spectroscopic studies near the proton drip line

Description: We have investigated nuclei close to the proton drip line by using heavy-ion fusion reactions to produce extremely neutron-deficient nuclides. Their nuclear decay properties were studied by using on-line isotope separators at Oak Ridge (UNISOR) and Berkeley (OASIS), the Oak Ridge National Laboratory velocity filter, and a fast helium-gas-jet transport system at Lawrence Berkeley Laboratory 88-Inch Cyclotron. Many isotopes, isomers, and {beta}-delayed-proton and {alpha}-particle emitters were discovered. This contribution summarizes three topics that are part of our overall program: decay rates of even-even {alpha}-particle emitters, mass excesses of {sup 181}Pb, {sup 182}Pb, and {sup 183}Pb, and {beta}-delayed proton emitters near N = 82. 14 refs., 6 figs.
Date: January 1, 1990
Creator: Toth, K.S. (Oak Ridge National Lab., TN (USA)); Moltz, D.M.; Nitschke, J.M.; Wilmarth, P.A. (Lawrence Berkeley Lab., CA (USA)) & Robertson, J.D. (Kentucky Univ., Lexington, KY (USA))
Partner: UNT Libraries Government Documents Department

Influence of nuclear structure on heavy-ion fusion at subbarrier energies

Description: Measurements of the cross section for fusion of projectiles of /sup 16/O and /sup 40/Ar with isotopes of Sm were made at energies below the fusion barrier. The experimental identification of the evaporation residues proceeds through the off-line detection of x-rays from radioactive product nuclei. Large differences are observed in the thresholds for fusion with vibrational and rotational target nuclei. 18 figures
Date: January 1, 1980
Creator: Stokstad, R.G.
Partner: UNT Libraries Government Documents Department

Preliminary evaluation of neutron capture cross sections for /sup 144/Sm, /sup 145/Sm and /sup 145/Pm

Description: We have made preliminary neutron-capture cross-section calculations of the Hauser-Feshbach type for the isotopes /sup 144/Sm, /sup 145/Sm, and /sup 145/Pm to investigate the production of radioactive /sup 145/Pm by neutron capture on the stable isotope /sup 144/Sm. The calculations were made for incident neutron energies from 2.5 MeV to about 1/sup -4/ or 10/sup -5/ MeV, wherever the first unbound resonance was estimated to occur in each case. At that energy, the calculated value was reduced by a somewhat arbitrary factor, and the excitation function extended down to thermal energy using a (E/sub n/)/sup -1/2/ energy dependence. Since very large uncertainties are associated with the position and magnitude of the first unbound resonance and the subsequent extrapolation back to thermal energy, the cross sections in this low-energy region should not be considered more accurate than +- a factor of 10. For incident neutron energies above each step, the calculations represent an average through the separated and overlapping resonance regions and may be accurate to better than +- a factor of 2. 18 refs., 7 figs., 5 tabs.
Date: February 13, 1986
Creator: Gardner, D.G. & Gardner, M.A.
Partner: UNT Libraries Government Documents Department

Few-nucleon transfer reactions on deformed nuclei

Description: Recent developments discussed include: alpha-transfer reactions on deformed nuclei, quasi-elastic neutron transfer reactions induced by /sup 58/Ni beams on spherical and deformed samarium nuclei, and the population of low-lying states in neutron rich nuclei using (particle,..gamma..) or (particle,e) coincidence methods. 37 refs., 10 figs. (LEW)
Date: January 1, 1985
Creator: van den Berg, A.M.
Partner: UNT Libraries Government Documents Department

Beta-delayed proton activities: /sup 147/Dy and /sup 149/Er

Description: The present paper discusses mainly the ..beta..-delayed proton spectra of /sup 147/Dy and of the hitherto unknown isotope, /sup 149/Er. However, following the submittal of the abstract for this conference we have now observed delayed protons following the decay of /sup 145/Dy. Additionally, we have identified a 0.5-s delayed-proton emitter and tentatively assign it to the new isotope, /sup 151/Yb.
Date: January 1, 1984
Creator: Toth, K.S.; Moltz, D.M.; Schloemer, E.C.; Cable, M.D.; Avignone, F.T. III & Ellis-Akovali, Y.A.
Partner: UNT Libraries Government Documents Department

Nuclear structure and reactions studied with the Darmstadt-Heidelberg crystal ball

Description: Angular momentum distribution in compound nuclei have been derived from ..gamma..-ray multiplicities and angular distributions measured with the Darmstadt-Heidelberg crystall ball. The influence of dynamic barrier fluctuation on the amount of angular momentum absorbed in the fusion process is discussed. Entrance channel effects have been observed which result in different decay paths for compound nuclei at the same excitation energy and spin in different target-projectile combinations. The ..gamma..-decay of resonances in the /sup 12/C + /sup 12/C system has been investigated. The measured ..gamma..-ray yields are consistently smaller than expected for collectively enhanced E2 transitions in a deformed and rigidly rotating intermediate system. The order of magnitude of the experimentally observed ..gamma..-intensity is, however, reproduced in theoretical calculations of nuclear bremsstrahlung, using realistic wave functions of the scattering states. 29 references, 10 figures.
Date: January 1, 1984
Creator: Metag, V.; Fischer, R.D.; Koch, G.; Kuehn, W.; Muehlhans, R.; Novotny, R. et al.
Partner: UNT Libraries Government Documents Department

Nuclear structure in deep-inelastic reactions

Description: The paper concentrates on recent deep inelastic experiments conducted at Argonne National Laboratory and the nuclear structure effects evident in reactions between super heavy nuclei. Experiments indicate that these reactions evolve gradually from simple transfer processes which have been studied extensively for lighter nuclei such as /sup 16/O, suggesting a theoretical approach connecting the one-step DWBA theory to the multistep statistical models of nuclear reactions. This transition between quasi-elastic and deep inelastic reactions is achieved by a simple random walk model. Some typical examples of nuclear structure effects are shown. 24 refs., 9 figs.
Date: January 1, 1986
Creator: Rehm, K.E.
Partner: UNT Libraries Government Documents Department