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On Closed Shells in Nuclei

Description: It has been suggested in the past that special numbers of neutrons or protons in the nucleus form a particularly stable configuration.{sup1} The complete evidence for this has never been summarized, nor is it generally recognized how convincing this evidence is. That 20 neutrons or protons (Ca{sup40}) form a closed shell is predicted by the Hartree model. A number of calculations support this fact.{sup2} These considerations will not be repeated here. In this paper, the experimental facts indicating a particular stability of shells of 50 and 82 protons and of 50, 82, and 126 neutrons will be listed.
Date: February 1, 1948
Creator: Mayer, M.G.
Partner: UNT Libraries Government Documents Department

Application of simple ramsauer model to neutron total cross sections

Description: The simple nuclear Ramsauer model has been used successfully to fit neutron cross sections for three decades, but has not been widely used because the foundations of the model seem to be so unrealistic. We have shown that the Glauber calculations with the inclusion of refraction and optical model calculations essentially validate this simple model for neutron total cross sections in the neutron energy range of 5-50 MeV. This model yields a simple formula for parameterizing the energy dependence of the neutron cross section. We have applied the model to nuclei ranging from vanadium to bismuth. With the addition of a single parameter, we can improve these fits to less than 1.5%.
Date: April 29, 1997
Creator: Bauer, R.W.; Anderson, J.D.; Grimes, S.M. & Madsen, V.A.
Partner: UNT Libraries Government Documents Department

Empirical model for shell-corrected level densities

Description: An empirical model for calculating level densities of closed and near- closed shell nuclei has been developed and tested. This method is based on the calculation of shell plus pairing corrections for each relevant nuclide. A new version of the ALICE code is used to extract these corrections from the Myers-Swiatecki mass formula and to apply them to the calculation of effective excitations in level densities. The corrections are applied in a backshifted fashion to assure correct threshold dependence. We compare our calculated results with experimental data for the production of 56Ni and 88Y to test shell corrections near f7/c closure and the N=50 neutron shell. We also compare our results with those using pure Fermi gas (plus pairing) level densities, and with the more computationally intensive model of Kataria and Ramamurthy.
Date: April 29, 1997
Creator: Ross, M.A. & Blann, M.
Partner: UNT Libraries Government Documents Department

Nuclear interaction potential in a folded-Yukawa model with diffuse densities

Description: The folded-Yukawa model for the nuclear interaction potential is generalized to diffuse density distributions which are generated by folding a Yukawa function into sharp generating distributions. The effect of a finite density diffuseness or of a finite interaction range is studied. The Proximity Formula corresponding to the generalized model is derived and numerical comparison is made with the exact results. (8 figures) (auth)
Date: September 1, 1975
Creator: Randrup, J.
Partner: UNT Libraries Government Documents Department

Finite range Droplet Model

Description: A treatment of nuclear masses and deformations is described which combines the Droplet Model with the folding model surface and Coulomb energy integrals. An additional exponential term, inspired by the folding model, but treated here as an independent contribution with two adjustable parameters, is included. With this term incorporated, the accuracy of the predicted masses and fission barriers was improved significantly, the ability of the Droplet Model to account for isotope shifts in charge radii was retained, and the tendency of the Droplet Model to over-predict the surface-tension squeezing of light nuclei was rectified. 20 references, 4 figures.
Date: August 1, 1984
Creator: Moeller, P.; Myers, W.D.; Swiatecki, W.J. & Treiner, J.
Partner: UNT Libraries Government Documents Department

Axial asymmetry, finite particle number and the IBA

Description: Although the IBA-1 contains no solutions corresponding to a rigid triaxial shape, it does contain an effective asymmetry. This arises from zero point motion in a ..gamma..-soft potential leading to a non-zero mean or rms ..gamma... Three aspects of this feature will be discussed: (1) The relation between IBA-1 calculations and the corresponding ..gamma... This point is developed in the context of the Consistent Q Formalism (CQF) of the IBA. (2) The dependence of this asymmetry on boson number, N, and the exploitation of this dependence to set limits on both the relative and absolute values of N for deformed nuclei. (3) The relation between this asymmetry and the triaxiality arising from the introduction of cubic terms into the IBA Hamiltonian. Various observables will be inspected in order both to determine their sensitivity to these two structural features and to explore empirical ways of distinguishing which origin of asymmetry applies in any given nucleus. 16 references.
Date: January 1, 1984
Creator: Casten, R.F.
Partner: UNT Libraries Government Documents Department


Description: Tables of gamma-ray transition probabilities predicted by the asymmetric rotor model of even-even nuclei were calculated. Tables are also presented on the coefficients of the rotational wave functions as a function of k, the asymmetry parameter. A third table gives the values of parameters needed to calculate energy levels in the hydrodynamical model using molecular spectroscopy tables. (C.J.G.)
Date: August 1, 1960
Creator: Day, P.P. & Mallmann, C.A.
Partner: UNT Libraries Government Documents Department


Description: The energy levels predicted by Davydov and Chaban's model were computed to compare theoretical predictions with experimental results. The computations were carried out for mu between 1.0, 0.90, 0.40, 0.35, and 0.1 and for gamma between 8, 9, 10, 12, 15, 20, 25, and 30 deg . (W.L.H.)
Date: November 1, 1960
Creator: Day, P.P.; Klema, E.D. & Mallmann, C.A.
Partner: UNT Libraries Government Documents Department


Description: The listing of a FORTRAN program for calculating the scattering of nucleons from a nonlocal optical potential is given. The mathematical formulation of the problem is presented, together with the numerical methods used in the code. The input to the program is explained, and a brief functional description of each subroutine of the code is included. (auth)
Date: July 11, 1963
Creator: Perey, F.G.
Partner: UNT Libraries Government Documents Department

Fractional Parentage Coefficients in Intermediate Coupling

Description: Fractional parentage coefficients are obtained which connect certain low- lying states in the 1p shell without the necessity of referring to either an LS or jj representation. The possibility of doing this algebraically is based on the generator method of producing the wave functions of these states. (auth)
Date: March 1, 1961
Creator: Kurath, D.
Partner: UNT Libraries Government Documents Department