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Observation of mean-spin barrier bump in sub-barrier fusion of sup 28 Si with sup 154 Sm

Description: We have measured the fusion excitation function and gamma-ray multiplicities, M{sub gamma}, for the {sup 28}Si + {sup 154}Sm system. We have also measured M{sub {gamma}} for the {sup 16}O + {sup 166} Er system that leads to the same compound nucleus, {sup 182}Os. This is used to calibrate the connection between M{sub {gamma}} and the first moment of the spin distribution of the compound nucleus, {l angle}{ell}{r angle}. We find that the deduced {l angle}{ell}{r angle} in {sup 28}Si + {sup 154}S… more
Date: January 1, 1990
Creator: Gil, S.; Abriola, D.; DiGregorio, D.E.; di Tada, M.; Elgue, M.; Etchegoyen, A. et al.
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Partner: UNT Libraries Government Documents Department
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Surrogate Reactions in the Actinide Region

Description: Over the past three years we have studied various surrogate reactions (d,p), ({sup 3}He,t), ({alpha},{alpha}{prime}) on several uranium isotopes {sup 234}U, {sup 235}U, {sup 236}U, and {sup 238}U. An overview of the STARS/LIBERACE surrogate research program as it pertains to the actinides is discussed. A summary of results to date will be presented along with a discussion of experimental difficulties encountered in surrogate experiments and future research directions.
Date: January 30, 2008
Creator: Burke, J. T.; Bernstein, L. A.; Scielzo, N. D.; Bleuel, D. L.; Lesher, S. R.; Escher, J. et al.
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Partner: UNT Libraries Government Documents Department
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Benchmarking the External Surrogate Ratio Method using the (alpha,alpha' f) reaction at STARS

Description: We measured the ratio of the fission probabilities of {sup 234}U* relative to {sup 236}U* formed via an ({alpha},{alpha}{prime}) direct reactions using the STARS array at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This ratio has a shape similar to the ratio of neutron capture probabilities from {sup 233}U(n; f) and {sup 235}U(n; f), indicating the alpha reactions likely formed a compound nucleus. This result indicates that the ratios of fission exit channel probabilitie… more
Date: January 9, 2008
Creator: Lesher, S. R.; Bernstein, L. A.; Ai, H.; Beausang, C. W.; Bleuel, D.; Burke, J. T. et al.
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Partner: UNT Libraries Government Documents Department
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Shape transitions in neutron-rich Ru isotopes: spectroscopy of 109,110,111,112Ru

Description: The spectroscopy of neutron-rich {sup 109,110,111,112}Ru nuclei was studied by measuring the prompt {gamma} rays originated from fission fragments, produced by the {sup 238}U({alpha},f) fusion-fission reaction, in coincidence with the detection of both fragments. For {sup 109,111}Ru, both the negative-parity (h{sub 11/2} orbitals) and positive-parity (g{sub 7/2} and/or d{sub 5/2} orbitals) bands were extended to substantially higher spin and excitation energy than known previously. The ground-s… more
Date: June 29, 2005
Creator: Hua, H.; Cline, D.; Hayes, A. B.; Teng, R.; Riley, D.; Clark, R. M. et al.
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Partner: UNT Libraries Government Documents Department
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Deducing the 237U(n,f) cross-section using the Surrogate Ratio Method

Description: The authors have deduced the cross section for {sup 237}U(n,f) over an equivalent neutron energy range from 0 to 20 MeV using the Surrogate Ratio method. A 55 MeV {sup 4}He beam from the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions: {sup 238}U({alpha},{alpha}{prime}f) and {sup 236}U({alpha},{alpha}{prime}f). The {sup 238}U reaction was a surrogate for {sup 237}U(n,f) and the {sup 236}U reaction was used as a surrogate for {sup … more
Date: December 29, 2005
Creator: Burke, J. T.; Bernstein, L. A.; Escher, J.; Ahle, L.; Church, J. A.; Dietrich, F. S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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New Results on Fission Cross Sections in Actinide Nuclei using the Surrogate Ratio Method and on Conversion Coefficients in Triaxial Strongly Deformed Bands in 167Lu from ICE Ball and Gammasphere

Description: The surrogate ratio technique is described. New results for neutron induced fission cross sections on actinide nuclei, obtained using this technique are presented. The results benchmark the surrogate ratio technique and indicate that the method is accurate to within 5% over a wide energy range. New results for internal conversion coefficients in triaxial strongly deformed bands in {sup 167}Lu are also presented.
Date: January 30, 2007
Creator: Beausang, C. W.; Lesher, S. R.; Burke, J. T.; Bernstein, L. A.; Phair, L.; Ai, H. et al.
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Partner: UNT Libraries Government Documents Department
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Surrogate Nuclear Reactions using STARS

Description: The results from two surrogate reaction experiments using the STARS (Silicon Telescope Array for Reaction Studies) spectrometer are presented. The surrogate method involves measuring the particle and/or {gamma}-ray decay probabilities of excited nuclei populated via a direct reaction. These probabilities can then be used to deduce neutron-induced reaction cross sections that lead to the same compound nuclei. In the first experiment STARS coupled to the GAMMASPHERE {gamma}-ray spectrometer succe… more
Date: October 26, 2004
Creator: Bernstein, L. A.; Burke, J. T.; Church, J. A.; Ahle, L.; Cooper, J. R.; Hoffman, R. D. et al.
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Partner: UNT Libraries Government Documents Department
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Deducing the 237U destruction cross-sections using the Surrogate Ratio Method

Description: We have deduced the destruction cross section of {sup 237}U via the (n, {gamma}) and (n,2n) reactions over an equivalent neutron energy range of 0 to 20 MeV using a new form of the Surrogate Ratio method [1-4] . The relative fission and neutron-evaporation decay probabilities of excited {sup 238}U populated via the ({alpha},{alpha}{prime}) inelastic scattering were measured using the silicon telescope array for reaction studies (STARS) coupled to the Livermore Berkeley array for collaborative e… more
Date: March 31, 2006
Creator: Bernstein, L. A.; Burke, J. T.; Ahle, L.; Church, J. A.; Escher, J.; Dietrich, F. S. et al.
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Partner: UNT Libraries Government Documents Department
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Population of Nuclei Via 7Li-Induced Binary Reactions

Description: The authors have investigated the population of nuclei formed in binary reactions involving {sup 7}Li beams on targets of {sup 160}Gd and {sup 184}W. The {sup 7}Li + {sup 184}W data were taken in the first experiment using the LIBERACE Ge-array in combination with the STARS Si {Delta}E-E telescope system at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory. By using the Wilczynski binary transfer model, in combination with a standard evaporation model, they are able to reproduc… more
Date: August 8, 2005
Creator: Clark, Rodney M.; Phair, Larry W.; Descovich, M.; Cromaz, Mario; Deleplanque, M. A.; Fall on, Paul et al.
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Partner: UNT Libraries Government Documents Department
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Population of Nuclei Via 7Li-Induced Binary Reactions

Description: The authors have investigated the population of nuclei formed in binary reactions involving {sup 7}Li beams on targets of {sup 160}Gd and {sup 184}W. The {sup 7}Li + {sup 184}W data were taken in the first experiment using the LIBERACE Ge-array in combination with the STARS Si {Delta}E-E telescope system at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory. By using the Wilczynski binary transfer model, in combination with a standard evaporation model, they are able to reproduc… more
Date: August 9, 2005
Creator: Clark, R. M.; Phair, L. W.; Descovich, M.; Cromaz, M.; Deleplanque, M. A.; Fallon, P. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Deducing the 237U(n,f) cross-section using the Surrogate Ratio Method

Description: The authors have deduced the {sup 237}U(n,f) cross-section over an equivalent neutron energy range of 0 to 20 MeV using the Surrogate Ratio method. A 55 MeV {sup 4}He{sup 2+} beam from the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions {sup 238}U({alpha},{alpha}'f) and {sup 236}U({alpha},{alpha}'f). The {sup 238}U reaction was a surrogate for {sup 237}U(n,f) and the {sup 236}U reaction was used as a surrogate for {sup 235}U(n,f).… more
Date: August 16, 2005
Creator: Burke, J. T.; Bernstein, L. A.; Escher, J.; Ahle, L.; Church, J. A.; Dietrich, F. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Very extended shapes in the A~;110 region

Description: High-angular-momentum states in {sup 108}Cd were populated via the {sup 64}Ni({sup 48}Ca,4n) reaction at a beam energy of 207 MeV. Gamma rays were detected using the Gammasphere array. A rotational band has been observed with a dynamic moment of inertia and deduced lower limit of the quadrupole moment suggesting a major-to-minor axis ratio larger than 1.8:1, placing it among the most deformed structures identified in any nucleus, to date.
Date: September 12, 2001
Creator: Clark, R. M.; Fallon, P.; Gorgen, A.; Cromaz, M.; Deleplanque, M. A.; Diamond, R. M. et al.
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Partner: UNT Libraries Government Documents Department
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Quadrupole moments of wobbling excitations in 163Lu

Description: Lifetimes of states in the triaxial strongly deformed bands of {sup 163}Lu have been measured in a Gammasphere experiment using the Doppler-shift attenuation method. The bands are interpreted as wobbling-phonon excitations from the characteristic electromagnetic properties of the transitions connecting the bands. Quadrupole moments were extracted for the 0-phonon yrast band and, for the first time, for the 1-phonon wobbling band. The very similar results found for both bands suggest a similar i… more
Date: January 1, 2004
Creator: Gorgen, A.; Clark, R. M.; Cromaz, M.; Fallon, P.; Hagemann, G. B.; Hubel, H. et al.
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Partner: UNT Libraries Government Documents Department
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Aspects of the Coriolis Interaction in U235

Description: We have performed three separate experiments at LBNL's 88-Inch Cyclotron over a period of several years in which {sup 235}U (thick target) was Coulomb-excited. It involved stand-alone experiments with Gammasphere and with the 8PI Spectrometer using {sup 136}Xe beams at 720 MeV, and a CHICO-Gammasphere experiment with an {sup 40}Ar beam at 180 MeV. In addition to extending the known negative-parity bands to high spin, we have assigned levels in some seven positive-parity bands which are in some … more
Date: January 1, 2005
Creator: Ward, D.; Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Diamond, R. M.; Fallon, P. et al.
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Partner: UNT Libraries Government Documents Department
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Searching for E(5) behavior in nuclei

Description: The properties of even-even nuclei with 30 {le} Z {le} 82, A {ge} 60 have been examined to find examples displaying the characteristics of E(5) critical-point behavior for the shape transition from a spherical vibrator to a triaxially soft rotor. On the basis of the known experimental state energies and E2 transition strengths, the best candidates that were identified are {sup 102}Pd, {sup 106,108}Cd, {sup 124}Te, {sup 128}Xe, and {sup 134}Ba. The closest agreement between experimental data and… more
Date: January 1, 2004
Creator: Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Descovich, M.; Diamond, R. M.; Fallon, P. et al.
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Partner: UNT Libraries Government Documents Department
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Order-to-chaos transition in rotational nuclei

Description: The authors have studied the narrow (valley-ridge) structure in the {gamma}-ray spectrum following a heavy-ion fusion reaction that produces several ytterbium nuclei. The intensity of this structure can be quantitatively related to the average chaotic behavior in these nuclei and they have traced this behavior from nearly fully ordered to nearly fully chaotic.
Date: May 13, 2004
Creator: Stephens, F. S.; Deleplanque, M. A.; Lee, I. Y.; Macchiavelli, A. O.; Ward, D.; Fallon, P. et al.
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Partner: UNT Libraries Government Documents Department
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In-beam gamma-ray spectroscopy of target fragmentation

Description: Fragmentation reactions, typically performed at energies {approx}E/A>50 MeV, produce neutron-rich nuclei but leave little angular momentum in the residues. In this work we have examined the product distribution and angular momentum input for a {sup 12}C beam at 30 MeV/A on a thick (40 mg/cm{sup 2}) target of {sup 51}V, testing the feasibility of in-beam gamma-ray spectroscopy study of target fragments at this lower energy. This technique allows the study of some neutron-rich nuclei to modera… more
Date: October 6, 2004
Creator: Rodriguez-Vieitez, E.; Lee, I. Y.; Ward, D.; Fallon, P.; Clark, R. M.; Cromaz, M. et al.
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Partner: UNT Libraries Government Documents Department
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Level structure of 141Ba and 139Xe and the level systematics of N=85 even-odd isotones

Description: New level schemes of {sup 141}Ba and {sup 139}Xe are proposed from the analyses of spontaneous-fission gamma data from our {sup 252}Cf spontaneous fission Gammasphere runs of 1995 and 2000. By analogy with the N = 85 even-odd isotones {sup 149}Gd, {sup 147}Sm, and {sup 145}Nd, spins and parities were assigned to the observed excited states in {sup 141}Ba and {sup 139}Xe. It appears that spherical shell model neutron excitations plus octupolephonons are an appropriate basis at the lower end of t… more
Date: January 31, 2002
Creator: Luo, Y. X.; Rasmussen, J. O.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Beyer, C. J. et al.
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Partner: UNT Libraries Government Documents Department
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Very extended shapes in 108Cd: evidence for the occupation of 'hyper-intruder' orbitals

Description: High-spin states in {sup 108}Cd were studied following the reaction {sup 64} Ni({sup 48}Ca,4n) at a beam energy of 207 MeV. Gamma rays were detected using the Gammasphere array. Two rotational bands have been observed at very high angular momentum. Measurements of fractional Doppler shifts yielded lower limits for the quadrupole moments and showed that the observed structures are at least as deformed as the superdeformed structures e.g. in the A {approx} 150 region, and possibly exceed a 2:1 ax… more
Date: July 1, 2002
Creator: Gorgen, A.; Clark, R. M.; Fallon, P.; Cromaz, M.; Deleplanque, M. A.; Diamond, R. M. et al.
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Partner: UNT Libraries Government Documents Department
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Damping in Yb nuclei

Description: In a mixture of three Yb nuclei, we find the rotational damping widths vary from 180 keV at 1.1 MeV {gamma}-ray energy to 290 keV at 1.5 MeV, and the average compound damping widths (or spreading widths) vary from 40 keV at 1.1 MeV {gamma}-ray energy to 60 keV at 1.3 MeV. The simulations also suggest extensive motional narrowing.
Date: July 1, 2002
Creator: Stephens, F. S.; Deleplanque, M. A.; Lee, I. Y.; Ward, D.; Fallon, P.; Cromaz, M. et al.
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Partner: UNT Libraries Government Documents Department
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The N=90 transitional nuclei {sup 150}Nd and {sup 152}Sm revisited

Description: The purpose of this paper is to show that recent data on the ground-state band and excited states based on the 0{sub 2}{sup +} level in {sup 15}Nd and {sup 152}Sm, especially the measured B(E2) values, can be well described by including a {Delta}K = 0 coupling between rotational bands. This is contrary to recent statements in the literature. The experimental data are compared with models which have supported the widely differing interpretations of these transitional nuclei. These interpretation… more
Date: January 21, 2003
Creator: Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Diamond, R. M.; Fallon, P.; Gorgen, A. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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