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Dynamical calculation of thresholds for compound-nucleus formation

Description: A necessary condition for forming a compound nucleus in a heavy-ion reaction is that the dynamical trajectory of the fusing system pass inside the fission saddle point in a multidimensional deformation space. For nuclear systems lighter than a critical size and for relatively low angular momentum, the fission saddle point lies outside the point of hard contact, and this requirement is automatically satisfied once a one-dimensional interaction barrier is overcome. However, for heavier nuclear sy… more
Date: January 1, 1983
Creator: Davies, K.T.R.; Sierk, A.J. & Nix, J.R.P
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Partner: UNT Libraries Government Documents Department
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Dynamical thresholds for complete fusion

Description: It is our purpose here to study the effect of nuclear dissipation and shape parametrization on dynamical thresholds for compound-nucleus formation in symmetric heavy-ion reactions. This is done by solving numerically classical equations of motion for head-on collisions to determine whether the dynamical trajectory in a multidimensional deformation space passes inside the fission saddle point and forms a compound nucleus, or whether it passes outside the fission saddle point and reseparates in a… more
Date: January 1, 1983
Creator: Davies, K. T. R.; Sierk, A. J. & Nix, J. R.
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Partner: UNT Libraries Government Documents Department
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Rapid disappearance of shell effects in the fission of transfermium nuclei

Description: In the last fifteen years we have learned that nuclear shells have a very broad and pervasive impact on the fission process. In the first few decades after the discovery of nuclear fission, the nucleus was treated as a drop of liquid with smoothly varying attractive and repulsive forces. Although this model still forms the underlying basis for fission, we also observe large effects from the superimposition of shell corrections derived from coupling the quantum states of individual nucleons. The… more
Date: January 1, 1983
Creator: Hulet, E. K.
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Partner: UNT Libraries Government Documents Department
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Pairing correction for particle-hole state densities

Description: The pairing correction proposed by Ignatyuk and Sokolov for particle-hole state densities has been examined. It has been found that the accuracy of the correction is sufficient for practical applications only if the system is in its normal state (..delta.. = 0). In the superfluid state (..delta.. not equal to 0), a consistent pairing-Pauli correction is developed here for improved accuracy. Practical implementations of the pairing correction are given and further developments are outlined.
Date: January 1, 1983
Creator: Fu, C.Y.
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Partner: UNT Libraries Government Documents Department
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Dynamical fusion thresholds in macroscopic and microscopic theories

Description: Macroscopic and microscopic results demonstrating the existence of dynamical fusion thresholds are presented. For macroscopic theories, it is shown that the extra-push dynamics is sensitive to some details of the models used, e.g. the shape parametrization and the type of viscosity. The dependence of the effect upon the charge and angular momentum of the system is also studied. Calculated macroscopic results for mass-symmetric systems are compared to experimental mass-asymmetric results by use … more
Date: January 1, 1983
Creator: Davies, K. T. R.; Sierk, A. J. & Nix, J. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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How do nuclei really vibrate or rotate

Description: By means of the adiabatic cranking model the properties of the current and velocity fields of nuclear quadrupole vibrations for even-even nuclei in the rare-earth region are investigated. BCS correlated wave functions based on the Nilsson single particle Hamiltonian have been used. The current fields are analyzed in terms of vector spherical harmonics. The realistic microscopic currents show a vortex structure not present in the classical irrotational flow. The microscopic origin of the vortex … more
Date: January 1, 1983
Creator: Andresen, H. G.; Kunz, J.; Mosel, U.; Mueller, M.; Schuh, A. & Wust, U.
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Partner: UNT Libraries Government Documents Department
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delta. /sub 33/ resonance in pion nucleus elastic, single, and double charge exchange scattering

Description: The ..delta../sub 33/ resonance is strongly excited in pion-nucleon scattering, but there is clearly only a limited amount of information that can be learned in scattering the pion from an isolated nucleon. One learns that there is a resonance of mass 1232 MeV, width 115 MeV, and, if one is willing to introduce a dynamical model, something about the off-shell extension of the amplitude. One stands to learn much more from pion-nucleus scattering because in this case the ..delta../sub 33/ resonan… more
Date: January 1, 1983
Creator: Johnson, M. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Delta-Nucleus Dynamics: Proceedings of Symposium

Description: The appreciation of the role in nuclear physics of the first excited state of the nucleon, the delta ..delta..(1232), has grown rapidly in the past decade. The delta resonance dominates nuclear reactions induced by intermediate energy pions, nucleons, and electromagnetic probes. It is also the most important non-nucleonic degree of freedom needed to resolve many fundamental problems encountered in the study of low-energy nuclear phenomena. Clearly, a new phase of nuclear physics has emerged and… more
Date: October 1, 1983
Creator: Lee, T. S. H.; Geesaman, D. F. & Schiffer, J. P.
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Partner: UNT Libraries Government Documents Department
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4. pi. data of relativistic nuclear collisions. [Plastic ball]

Description: During the past two years, complete events of relativistic nuclear collisions are being studied with the Plastic Ball, the first electronic nonmagnetic particle-identifying 4..pi.. spectrometer. It is well suited to handle the large multiplicities in these reactions and allows collection of data at a rate sufficient to make further software selections to look at rare events. The analysis of the data follows various lines covering topics like thermalization, stopping or transparency, cluster-pro… more
Date: May 1, 1983
Creator: Gutbrod, H.H.; Gustafsson, H.A. & Kolb, B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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SO/sub 8/ model of collectivity in nuclei

Description: The interacting boson model (IBM) has been very successful in giving a unified and simple description of the spectroscopic properties of a wide range of nuclei, from vibrational through rotational nuclei. The three basic assumptions of the model are that (1) the valence nucleons move about a doubly closed core, (2) the collective low-lying states are composed primarily of coherent pairs of neutrons and pairs of protons coupled to angular momentum zero and two and (3) these coherent pairs are ap… more
Date: January 1, 1983
Creator: Ginocchio, J.N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Pion production at 180/sup 0/ in nucleus-nucleus collisions

Description: A survey experiment of pion production at 180/sup 0/ in nucleus-nucleus collisions is presented. Beams of 1.05 GeV/A and 2.1 GeV/A protons, alphas, and carbon were used, as well as proton beams of 0.80 GeV, 3.5 GeV, and 4.89 GeV, and argon beams of 1.05 GeV/A and 1.83 GeV/A. This is the first such experiment to use the heavier beams. Targets used ranged from carbon to lead. An in-depth review of the literature, both experimental and theoretical, is also presented. The systematics of the data ar… more
Date: May 1, 1983
Creator: Chessin, S.A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Covariances for neutron cross sections calculated using a regional model based on local-model fits to experimental data

Description: We suggest a procedure for estimating uncertainties in neutron cross sections calculated with a nuclear model descriptive of a specific mass region. It applies standard error propagation techniques, using a model-parameter covariance matrix. Generally, available codes do not generate covariance information in conjunction with their fitting algorithms. Therefore, we resort to estimating a relative covariance matrix a posteriori from a statistical examination of the scatter of elemental parameter… more
Date: November 1, 1983
Creator: Smith, D. L. & Guenther, P. T.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Effect of the. delta. (1236) resonance on magnetic dipole properties of nuclei

Description: The effect of the ..delta..(1236) resonance on magnetic moments, M1 transition rates and beta decay is discussed. The main effect of including this resonance is to renormalize the g-factor of the valence nucleons and explicit values for this renormalization are given. The effect on l-forbidden M1 transitions is investigated.
Date: January 1, 1983
Creator: Lawson, R.D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Code ALICE B and B: a precompound/evaporation fission code emphasizing neutron yields

Description: This report describes a version of the code ALICE/LIVERMORE 82 which has been modified to output neutron yield information of the type one would measure in an experiment gated by measuring a fission fragment. The modified code does the same precompound/compound decay calculations as the code ALICE/LIVERMORE 82, but has additional buffers and algorithms for the neutron yield calculation. We calculate the pre-fission neutron spectra and multiplicities, and post-fission neutron spectra and multipl… more
Date: November 1, 1983
Creator: Blann, M. & Howe, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Ultra-relativistic heavy ions and cosmic rays

Description: The collisions of ultra-relativistic heavy ions, E/sub /N/ greater than or equal to 1 TeV/nucleon are most interesting, since, at these energies, matter is produced at sufficiently high energy density that a quark-gluon plasma has a good chance to form. Very heavy ions are also most interesting since the matter forms in a larger volume than for light ions, and the matter is at a somewhat higher energy density. At very high energies with very heavy ions there is great flexibility in the experime… more
Date: May 1, 1983
Creator: McLerran, L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Boson-mediated interactions between static sources

Description: The techniques are now available for doing accurate computations of static potentials arising from the exchange of virtual mesons. Such computations must take account of the fact that different approximation methods must be used in the regions where R is large and where R is small. In the asymptotic region, the distorted-field approximation provides an appropriate starting-point, but it must be improved before trustworthy results are obtained for all but the largest values of R. In the region o… more
Date: January 1, 1983
Creator: Bolsterli, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Prompt fission neutron spectra and average prompt neutron multiplicities

Description: We present a new method for calculating the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity anti nu/sub p/ as functions of the fissioning nucleus and its excitation energy. The method is based on standard nuclear evaporation theory and takes into account (1) the motion of the fission fragments, (2) the distribution of fission-fragment residual nuclear temperature, (3) the energy dependence of the cross section sigma/sub c/ for the inverse process of compound-nucleus… more
Date: January 1, 1983
Creator: Madland, D. G. & Nix, J. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Quark distributions in nuclei: results from lepton probes

Description: Deep inelastic lepton scattering from nuclei indicates that quark-parton distributions are significantly different from the distributions in isolated nucleons. The EMC and SLAC data on iron and deuterium targets show enhanced and suppresed scattering for kinematic regions where Bjorken x < 1. In addition, the SLAC data on /sup 3/He show strong enhancement over results with conventional nuclear theory for x > 1. These data and recent model interpretations are summarized. Detailed comparisons wit… more
Date: January 1, 1983
Creator: Vary, J.P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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