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Review of (n; n',. gamma. ) cross-section data on actinide nuclei

The available high-resolution (n;n',..gamma..) cross section data on actinide nuclei, essentially /sup 238/U and /sup 232/Th, are reviewed by dividing the measurement process into two steps. First, the measurement of discrete photon production cross sections is discussed by comparing white and monoenergetic neutron source techniques. Resultant cross sections are compared and their accuracies assessed. Second, the step of inferring inelastic scattering cross sections from photon production cross… more

Date: January 1, 1981

Creator: Olsen, D.K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Determining (n,f) cross sections for actinide nuclei indirectly: An examination of the Surrogate Ratio Method

The validity of the Surrogate Ratio method for determining (n,f) cross sections for actinide nuclei is examined. This method relates the ratio of two compound-nucleus reaction cross sections to a ratio of coincidence events from two measurements in which the same compound nuclei are formed via a direct reaction. With certain assumptions, the method allows one of the cross sections to be inferred if the other is known. We develop a nuclear reaction-model simulation to investigate whether the ass… more

Date: May 22, 2006

Creator: Escher, J E & Dietrich, F S

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Strength of Coriolis Coupling in actinide nuclei

Coriolis Coupling V/sub cor/ plays an important role in deformed nuclei. V/sub cor/ is proportional to h/sup 2//J(j (j + 1) -..cap omega.. (..cap omega.. + 1))/sup 1/2/ and therefore is particularly significant in the nuclei with large j and low ..cap omega.. Nilsson levels close to Fermi surface: n(i/sub 13/2/) in A = 150 to 170 rare-earth nuclei and p(i/sub 13/2/) and n(j/sub 15/2/) in A greater than or equal to 224 actinide nuclei. Because of larger j (n(j/sub 15/2/) versus n(i/sub 13/2/)) a… more

Date: January 1, 1982

Creator: Peker, L. K.; Rasmussen, J. O. & Hamilton, J. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Experimental level-structure determination in odd-odd actinide nuclei

The status of experimental determination of level structure in odd-odd actinide nuclei is reviewed. A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei is applied to actinide species where new experimental data have been obtained by use of neutron-capture gamma-ray spectroscopy. The input parameters required for the calculation are derived from empirical data on single-particle excitations in neighboring odd-mass nuclei. Calculated con… more

Date: April 4, 1985

Creator: Hoff, R.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Octupole effects at super and normal deformation.

This presentation deals with recent results on the onset of octupole collectivity in superdeformed nuclei of the A {approx} 190 and A {approx} 150 regions as well as in actinide nuclei at normal deformation. It is shown that most of the properties of these negative parity sequences can be understood in terms of Random Phase Approximation (RPA) calculations, although the observations in some Pu isotopes continue to be a challenge to interpret.

Date: June 6, 2002

Creator: Janssens, R. V. F.

Item Type: 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

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.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Distribution of independent fission-product yields to isomeric states

A simple one-parameter model is presented for calculating the distribution of independent yield strength between ground and isomeric states of primary fission products formed by neutron-induced fission of actinide nuclei. Yield branching ratios are calculated as a function of neutron energy (thermal, fast, and 14-MeV) for 144 nuclides having isomeric states with T/sub 1/2/ greater than or equal to 0.1 s. The results are proposed for use in the ENDF/B-V yield files.

Date: November 1, 1976

Creator: Madland, D. G. & England, T. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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A parameter study of the r process

We consider the r-process production of actinide nuclei from a high temperature nucleon gas in a model which is most favorable for the r process. In this way, we can place upper limits on the value of the free electron fraction, Y/sub e/, of the material which experiences the r process. We find that for a broad range of initial nucleon densities, Y/sub e/ must be small (close to that for equilibrium neutron star matter). 11 refs., 2 figs.

Date: September 1, 1987

Creator: Sale, K. E. & Mathews, G. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Photofission and electrofission. [Review, cross sections, fission yield, angular distribution]

Recent experimental progress in the fields of photofission and electrofission of actinide nuclei is summarized. In particular, experimental results which throw light on the delineation of the characteristics of the giant resonances are highlighted. Measurements of especial interest in this regard include photofission cross-section studies with monoenergetic photons and electrofission yield and angular-distribution studies. 36 references.

Date: August 17, 1978

Creator: Berman, B.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Comments on nuclear physics for gamma-ray lasers

Estimates are presented of the probability of finding a closely spaced pair of levels, one member of which is an isomer, in the rare earth and actinide nuclei. A discussion of the typical electromagnetic transition strengths expected between such pairs is given. Present and future experimental techniques are described, including the possible development of particle detectors with greatly improved resolution. 17 refs., 1 tab.

Date: October 1, 1985

Creator: Dietrich, F.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fast and slow fission

Measurements of alpha particle induced fission of actinide nuclei and fission of the composite system /sup 170/Yb formed in /sup 12/C and /sup 20/Ne bombardments both show significantly greater neutron emission prior to fission than is consistant with current statistical models. Implications of these results are discussed in the context of possible extreme models: (1) the enhancement of fission at low excitation energies due to shell effects; (2) the inhibition of fission at high excitations du… more

Date: January 1, 1981

Creator: Britt, H. C. & Gavron, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Studies of fast neutron inelastic scattering to vibrational states of the actinide nuclei /sup 232/Th and /sup 238/U by the Lowell Group (experimental and theoretical)

A survey is presented of the Lowell group's latest experimental and theoretical results for the inelastic scattering of fast neutrons to vibrational states of the deformed actinide nuclei /sup 232/Th and /sup 238/U. Excitation functions are shown from 0.8 to 2.5 MeV; angular distributions have been determined at 1.2 MeV and 1.5 MeV. The theoretical curves have been calculated using the standard (CN + DI) and unified (statistical S-matrix) formalisms. Generally good agreement has been found to p… more

Date: January 1, 1983

Creator: Sheldon, E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Complex fragments from excited actinide nuclei: A new test of the finite range model

Complex fragments ranging in charge from 7less than or equal toZless than or equal to45 have been detected in binary coincidence following the reaction of 8.4 MeV/u/sup 232/Th+/sup 12/C, and are shown to arise from the binary decay of a /sup 244/Cm compound nucleus. This work confirms earlier radiochemical observations of very light fragments in the fission fragment mass distribution, establishes their binary character, and interprets their yield in terms of finite range potential energy barrie… more

Date: May 1, 1988

Creator: Sarantities, D. G.; Bowman, D. R.; Wozniak, G. J.; Charity, R. J.; Liu, Z. H.; McDonald, R. J. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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SURFACE SYMMETRY ENERGY OF NUCLEAR ENERGY DENSITY FUNCTIONALS

We study the bulk deformation properties of the Skyrme nuclear energy density functionals. Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band-heads in Hg and Pb isotopes, and fission isomers in actinide nuclei. After subtra… more

Date: December 20, 2010

Creator: Nikolov, N.; Schunck, N.; Nazarewicz, W.; Bender, M. & Pei, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Unsafe coulomb excitation of {sup 240-244}Pu.

The high spin states of {sup 240}Pu and {sup 244}Pu have been investigated with GAMMASPHERE at ATLAS, using Coulomb excitation with a {sup 208}Pb beam at energies above the Coulomb barrier. Data on a transfer channel leading to {sup 242}Pu were obtained as well. In the case of {sup 244}Pu, the yrast band was extended to 34{h_bar}, revealing the completed {pi}i{sub 13/2} alignment, a ''first'' for actinide nuclei. The yrast sequence of {sup 242}Pu was also extended to higher spin and a similar b… more

Date: December 1, 1998

Creator: Wiedenhoever, I.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Dipole strength functions in the actinide mass region

We have calculated a number of neutron- and photon-induced reactions for the actinide nuclei /sup 232/Th, /sup 238/U, and /sup 237/Np. By fitting average resonance capture (ARC) measurements and total neutron capture data, we deduced absolute dipole strength functions for /sup 233/Th and /sup 239/U. We have found that the M1/E1 ratio is the same as in the /sup 176/Lu case, but the total transition strength was larger by about 27%. 17 refs., 4 figs., 1 tab.

Date: July 15, 1987

Creator: Gardner, D. G.; Gardner, M. A. & Hoff, R. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fast electric dipole transitions in Ra-Ac nuclei

Lifetime of levels in /sup 225/Ra, /sup 225/Ac, and /sup 227/Ac have been measured by delayed coincidence techniques and these have been used to determine the E1 gamma-ray transition probabilities. The reduced E1 transition probabilities. The reduced E1 transition probabilities in /sup 225/Ra and /sup 225/Ac are about two orders of magnitude larger than the values in mid-actinide nuclei. On the other hand, the E1 rate in /sup 227/Ac is similar to those measured in heavier actinides. Previous st… more

Date: January 1, 1985

Creator: Ahmad, I.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Benchmarking the External Surrogate Ratio Method using the (alpha,alpha' f) reaction at STARS

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.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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In-beam studies of high-spin states of actinide nuclei

High-spin states in the actinides have been studied using Coulomb- excitation, inelastic excitation reactions, and one-neutron transfer reactions. Experimental data are presented for states in {sup 232}U, {sup 233}U, {sup 234}U, {sup 235}U, {sup 238}Pu and {sup 239}Pu from a variety of reactions. Energy levels, moments-of-inertia, aligned angular momentum, Routhians, gamma-ray intensities, and cross-sections are presented for most cases. Additional spectroscopic information (magnetic moments, M… more

Date: November 15, 1990

Creator: Stoyer, M.A. (Lawrence Berkeley Lab., CA (USA). Nuclear Science Div. California Univ., Berkeley, CA (USA). Dept. of Chemistry)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Applied nuclear data research and development. Progress report, January 1-March 31, 1981

Activities of the Los Alamos Nuclear Data Group for January 1 through March 31, 1981, are described. Topics include: (1) peripheral effects in R-matrix theory; (2) Coulomb corrections in light nuclei; (3) new R-matrix analysis of reactions in the /sup 7/Li system; (4) variance-covariance analysis of n + Li reactions; (5) calculated charged-particle emission in the mass-90 region; (6) determination of deformed optical model parameters for neutron reactions on /sup 235/U and /sup 239/Pu; (7) calc… more

Date: July 1, 1981

Creator: Baxman, C.I. & Young, P.G. (comps.)

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Unsafe Coulomb excitation of {sup 240-244}Pu.

The high spin states of {sup 240}Pu and {sup 244}Pu have been investigated with GAMMASPHERE at ATLAS, using Coulomb excitation with a {sup 208}Pb beam at energies above the Coulomb barrier. Data on a transfer channel leading to {sup 242}Pu were obtained as well. In the case of {sup 244}Pu, the yrast band was extended to 34{h_bar} revealing the completed {pi}i{sub 13/2} alignment, a ''first'' for actinide nuclei. The yrast sequence of {sup 242}Pu was also extended to higher spin and a similar ba… more

Date: February 4, 1999

Creator: Ahmad, I.; Amro, H.; Carpenter, M. P.; Chowdhury, P.; Cizewski, J.; Cline, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Some reminiscences of the early days of californium

The discovery of /sup 252/Cf production in the Mike explosion is reviewed. (DLC)

Date: May 1, 1983

Creator: Ghiorso, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Early history of heavy isotope research at Berkeley, August 1940 to April 1942

A day-to-day account of the work done at Berkeley during August 1940 to April 1942 on the discovery of plutonium and on the isotope /sup 233/U is given. (LK)

Date: June 1, 1976

Creator: Seaborg, G. T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Nuclear design of fast hybrid blankets

The objective of this presentation is to: (1) present the physical motivation for fusion-fission hybrids, (2) outline design considerations for hybrid blankets, and (3) discuss the nuclear performance potential of hybrid blankets.

Date: January 23, 1978

Creator: Lee, J. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department