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Location of a doorway state using the channel n + /sup 207/Pb

Description: The location of a doorway state in the n + /sup 207/Pb channel is established through a statistical analysis of the observed partial widths for gamma-rays and neutrons. Several statistical tests developed to help locate doorway states are presented. The statistical analysis focuses on the strong correlation between large partial widths in the two exit channels. Widths in both exit channels exhibit extremely large values in the energy region near E/sub n/ = 120 keV. This clustering of large widths, even when considered separately for each exit channel, is relatively unlikely to occur in a statistical sample. The strong correlation between channels decreases the likelihood for this clustering of large widths to occur in a statistical sample to less than 0.0003.
Date: January 1, 1984
Creator: Dennis, L.C. & Raman, S.
Partner: UNT Libraries Government Documents Department

Introduction to the study of collisions between heavy nuclei

Description: Current investigations concerning the collisions of nuclei governed by small de Broglie wavelengths are reviewed. The wave packets localize nuclei in regions small compared to their diameters. Cross sections are examined for potential scattering, elastic scattering, quasi-molecular states, peripheral particle-transfer reactions, fusion, and deep inelastic collisions. Theories of fusion and deep inelastic collisions are summarized. This paper is in the nature of a review-tutorial. 45 references, 51 figures, 2 tables. (RWR)
Date: January 1, 1980
Creator: Bayman, B.F.
Partner: UNT Libraries Government Documents Department

Studies of heavy ion reactions and transuranic nuclei. Progress report, August 1, 1979-July 31, 1980. [Univ. of Rochester, New York, 8/1/79-7/31/80]

Description: The study of heavy-ion reaction mechanisms at the SuperHILAC and LAMPF is reported. Preprints of five articles and manuscripts of four recent conference papers are given, along with complete citations of publications and a list of personnel. Significant work was performed in the following areas: the bombarding energy dependence of the /sup 209/Bi + /sup 136/Xe reaction; the fragment yields for specific Z and A for projectile-like fragments produced in the reaction of 8.3-MeV/u /sup 56/Fe ions with targets of /sup 56/Fe, /sup 165/Ho, /sup 209/Bi, and /sup 238/U; and time distributions of fragments from delayed fission after muon capture for muonic /sup 235/U, /sup 238/U, /sup 237/Np, /sup 239/Pu, and /sup 242/Pu. (RWR)
Date: July 1, 1980
Creator: Huizenga, J.R.
Partner: UNT Libraries Government Documents Department

Giant multipole resonances: perspectives after ten years

Description: Nearly ten years ago evidence was published for the first of the so-called giant multipole resonances, the giant quadrupole resonance. During the ensuing years research in this field has spread to many nuclear physics laboratories throughout the world. The present status of electric giant multipole resonances is reviewed. 24 figures, 1 table.
Date: January 1, 1980
Creator: Bertrand, F.E.
Partner: UNT Libraries Government Documents Department

Multipole matrix elements for /sup 208/Pb

Description: New measurements of inelastic proton scattering to low-lying states of /sup 208/Pb at 200 and 400 MeV are reported. Deformation lengths extracted from angular distributions for the 3/sup -/ (2.614 MeV), 5/sub 1//sup -/ (3.198 MeV), 5/sub 2//sup -/ (3.209 MeV), 2/sup +/ (4.086 MeV) and 4/sup +/ (4.324 MeV) states are in good accord with values extracted at other incident proton energies. The fact that the deformation lengths are independent of incident proton energy within experimental uncertainty provides support for the validity of the collective DWBA for medium energy proton scattering to strongly excited states. Advantage is taken of this to extract statistically more precise values of the ratio of neutron to proton multipole matrix elements (M/sub n//M/sub p/). Different methods of determining the appropriate average value of M/sub n//M/sub p/ are discussed. 3 refs., 1 tab.
Date: January 1, 1986
Creator: McDaniels, D.K.; Lisantti, J.; Swenson, L.W.; Chen, X.Y.; Bertrand, F.E.; Gross, E.E. et al.
Partner: UNT Libraries Government Documents Department

Dynamical limitations to heavy-ion fusion

Description: In spite of the many attempts to synthesize superheavy elements in recent years, these efforts have not yet been successful. Recent improved theoretical models of heavy-ion fusion reactions suggest that the formation of super-heavy elements is hindered by the dynamics of the process. Several recent experiments lend support to these theories. The necessity of an excess radial velocity (extra push) over the Coulomb barrier in order to induce fusion is observed experimentally as predicted by the theory. So is a new reaction mechanism, called quasi-fission which tend to exhaust the part of the reaction cross section, which would otherwise lead to fusion. The present study shows that the angular distribution of fragments from quasi-fission processes are very sensitive to the occurrence of this reaction mechanism. A slight modification of one parameter in the theory demanded by the observation of quasi-fission for lighter projectiles via the angular distributions, has the consequence of posing even more-stringent limitations on heavy-ion-fusion reactions. This reduces even further the possibility for synthesizing and identifying superheavy elements in heavy-ion-fusion reactions.
Date: January 1, 1983
Creator: Back, B.B.
Partner: UNT Libraries Government Documents Department

Multifragmentation in intermediate energy heavy ion collisions

Description: The system 200 MeV/nucleon Au + Au was studied, giving full azimuthal coverage for intermediate mass fragments in the forward hemisphere in the center of mass system while measuring all the light particles in each event. The complete measurement of light particles (p, d, t, /sup 3/He, /sup 4/He) allows determination of the charge multiplicity of participant baryons, which increases as the impact parameter between the projectile and target nuclei gets smaller. This quantity was used to sort the events into groups according to impact parameter. It is found that peripheral collisions give rise to fragments with rapidities very close to the beam rapidity. It is also observed that the transition between the peripheral and central collisions is very smooth, with a gradual shift in the rapidities of the observed fragments away from the projectile rapidity. The total intermediate mass fragment multiplicity is found to increase with increasing participant baryon charge multiplicity. 7 refs., 2 figs. (LEW)
Date: January 1, 1986
Creator: Jacak, B.V.; Britt, H.C.; Gavron, A.I.; Wilhelmy, J.; Claesson, G.; Doss, K.G.R. et al.
Partner: UNT Libraries Government Documents Department

Nuclear Moments and Nuclear Structure. Annual Progress Report, August 1, 1979-July 31, 1980. [Johns Hopkins Univ. , Baltimore, 8/1/79-7/31/80]

Description: Activities of the period August 1, 1979 through July 31, 1980 are reviewed. The results from the relativistic heavy-ion central collisions from the Bevatron are updated, and now represent the most recent evaluation of an energy scan in a search for phase transitions in nuclear matter. The effective cross section for the pion production and additional information, incuding the multiplicity distributions and ..pi..-..pi.. correlations, are obtained. Preparation is underway for an approved experiment using heavier projectiles at the Bevalac, searching for the unusual production of high energy gamma-rays and lepton pairs as signatures for neutral mesons. The importance of such events as an evidence of the onset of phase transition is discussed. A brief summary is given for an alpha-alpha collision experiment at the CERN ISR in the search for unusual behavior in secondary hadron production. The measurement of the pionic x-rays using a bent crystal spectrometer is now analyzed to yield the new value for pionic mass, and upper limit for the muonic neutrino mass. Preparation is underway for the approved experiment at the TRIUMF for the study of the neutron and gamma ray correlation in ..pi.. capture. 18 figures, 5 tables. (RWR)
Date: January 1, 1980
Creator: Madansky, L. & Lee, Y. K.
Partner: UNT Libraries Government Documents Department

Giant resonances - why protons

Description: Protons excite giant resonances, indeed the systematic establishment of the existence of the first non-dipole giant resonance, the giant quadrupole resonance (GQR) came from the use of inelastic proton scatering. The question addressed, however, is how does the proton stack up for such studies when compared to the use of other hadronic probes. What can we uniquely learn about giant multipole resonances using proton scattering. Specifically, results from (p, p'), and (..cap alpha.., ..cap alpha..') and (/sup 16/o, /sup 16/O') reactions are compared as regards excitation of giant multipole resonances, and some of the advantages and disadvantages to the use of each probe are detailed. It is hoped to leave the impression that it is in the determination of resonance multipolarity by comparison of measured and calculated angular distributions that the proton is a winner. It is shown what we are learning about high-L (L > 3) giant resonances using the (p, p') angular distribution. This discussion will generally be limited to isoscalar electric (i.e., T = 0, S = 0) giant resonances.
Date: January 1, 1983
Creator: Bertrand, F.E.
Partner: UNT Libraries Government Documents Department

Nuclear chemistry progress report, September 1, 1978-August 31, 1979. [Oregon State Univ. , September 1, 1978-September 1, 1979]

Description: Work done between September 1, 1978, and September 1, 1979, involved the study of low-energy and relativistic heavy-ion reactions. In the former area most of the effort went into a careful re-examination of the failure to synthesize superheavy elements in complete fusion reactions. It was concluded that fission barriers are of the order of 5 or 6 MeV corresponding to a half-life of 10/sup 5/ years, a value precluding their occurrence in nature. In the area of relativistic heavy-ion (RHI) reaction studies, the most interesting results came in studies of the energy dependence of the product mass and charge distributions resulting from the interaction of RHIs with U and studies of the recoil properties of the target residues produced in the reaction of RHIs with heavy targets. Lists of personnel, publications, and oral presentations are included, along with a collection of reprints and preprints. Eight of the individual articles in this report are indexed separately.
Date: January 1, 1979
Creator: Loveland, W.D.
Partner: UNT Libraries Government Documents Department

Search for flow in the reaction Ar + Pb. [0. 8 GeV/u]

Description: Interactions between Ar projectiles and lead are studied in terms of global observables. The Streamer Chamber at the Berkeley BEVALAC was used to record all charged particles produced in collisions between 0.8 GeV/u Ar projectiles with a Pb/sub 3/O/sub 4/ target. A hardware trigger selected central collisions with Pb nuclei corresponding to a trigger cross section of 1 barn. In a geometrical picture this is equivalent to an impact parameter range of 0 to 5 fm.
Date: August 1, 1983
Creator: Renfordt, R.E.; Brockmann, R.; Harris, J.W.; Maier, M.; Riess, F.; Sandoval, A. et al.
Partner: UNT Libraries Government Documents Department

Angular distributions of target fragments from the reactions of 292 MeV - 25. 2 GeV /sup 12/C with /sup 197/Au and /sup 238/U

Description: Angular distributions of target fragments from the reactions of /sup 12/C with /sup 197/Au and /sup 238/U were measured at projectile energies of 292 MeV, 1.0 GeV, 3.0 GeV, 12.0 GeV and 25.2 GeV. The angular distributions of the /sup 197/Au target fragments were all forwardly peaked. Extensively forward peaked angular distributions were observed at the non-relativistic projectile energies (292 MeV, 1.0 GeV). No obvious differences were observed in the angular distributions at the different relativistic projectile energies of 3.0 GeV, 12.0 GeV and 25.2 GeV. The characteristic angular distribution pattern from the relativistic projectile energy experiments was also observed in the non-relativistic energy experiments. Maximum degree of forward-peaking in the angular distributions at each projectile energy was observed at the product mass number (A) around 190 from the 292 MeV projectile energy, at A=180 from 1.0 GeV and at A=175 from 3.0 GeV and 12.0 GeV. In general, two different types of angular distributions were observed in the relativistic projectile energy experiments with the /sup 238/U target. Isotropic angular distributions were observed for the fission product nuclides. The angular distributions of the fission products at the intermediate (292 MeV) energy showed slightly forward- peaked angular distributions. Because of the long projectile-target interaction time in the primary nuclear reaction, larger momentum was transferred from the projectile to the target nucleus. Steep forward-peaked angular distributions were also observed with the /sup 238/U target.
Date: May 20, 1983
Creator: Morita, Y.
Partner: UNT Libraries Government Documents Department

Flow of nuclear matter

Description: The systems Nb + Nb and Au + Au have been measured at different energies at the Bevalac with the Plastic Ball spectrometer. Distributions of the flow angles as a function of charged particle multiplicity are presented. Also shown is a transverse momentum analysis for 400 MeV per nucleon Nb + Nb. 25 refs., 5 figs., 1 tab.
Date: August 1, 1985
Creator: Ritter, H.G.; Doss, K.G.R.; Gustafsson, H.A.; Gutbrod, H.H.; Kampert, K.H.; Kolb, B. et al.
Partner: UNT Libraries Government Documents Department

Polarization transfer in inelastic scattering and pionic models of the EMC effect

Description: The aim of the experiment reported was to make a precise test of the enhanced pion field model in a medium-energy scattering experiment. The quantity probed is the spin-longitudinal response function, a measure of the nuclear pion density which is used explicitly in the pion-excess models of the EMC effect. The point of reference used is deuterium. The spin-dependent response functions for heavy targets and /sup 2/H are compared using identical experimental techniques. The technique of complete polarization transfer is used to separate the spin-longitudinal and spin-transverse response in the continuum. The experiment consisted of precise determinations of the polarization transfer coefficients for 500 MeV protons inelastically scattered from Pb, Ca, and /sup 2/H. The experiment utilized longitudinal, sideways, and normal polarized beams in conjunction with final polarization analysis from the focal-plane polarimeter of the high-resolution spectrometer. Quantities constructed from these data are the longitudinal and transverse spin-flip probabilities. Calculations were performed of the ratio of longitudinal to transverse response functions and of the EMC effect with the same model. No evidence was found for collectivity in the isovector spin-longitudinal response function. 10 refs. (LEW)
Date: January 1, 1985
Creator: Carey, T.A.; Jones, K.W.; McClelland, J.B.; Moss, J.M.; Rees, L.B.; Tanaka, N. et al.
Partner: UNT Libraries Government Documents Department

Study of transfer and breakup reactions with the plastic box

Description: The study of transfer reactions with heavy-ion projectiles is complicated by the frequent presence of three or more nuclei in the final state. One prolific source of three-body reactions is the production of a primary ejectile in an excited state above a particle threshold. A subset of transfer reactions, viz., those producing ejectiles in bound states, can be identified experimentally. This has been accomplished with a 4..pi.. detector constructed of one-millimeter-thick scintillator paddles of dimension 20 cm x 20 cm. The paddles are arranged in the form of a cube centered around the target with small entrance and exit apertures for the beam and the projectile-like fragments, (PLF). The detection of a light particle (e.g., a proton or an alpha particle) in coincidence with a PLF indicates a breakup reaction. The absence of any such coincidence indicates a reaction in which all the charge lost by the projectile was transferred to the target. With this technique we have studied the transfer and breakup reactions induced by 220 and 341 MeV /sup 20/Ne ions on a gold target. Ejectiles from Li to Ne have been measured at several scattering angles. The absolute cross sections, angular distributions and energy spectra for the transfer and breakup reactions are presented. Relatively large cross sections are observed for the complete transfer of up to seven units of charge (i.e., a nitrogen nucleus). The relatively large probabilities for ejectiles to be produced in particle-bound states suggest that on the average, most of the excitation energy in a collision resides in the heavy fragment when mass is transferred from the lighter to the heavier fragment. The gross features and trends in the energy spectra for transfer and breakup reactions are similar. 20 references.
Date: December 1, 1984
Creator: Stokstad, R.G.; Albiston, C.R.; Bantel, M.; Chan, Y.; Countryman, P.J.; Gazes, S. et al.
Partner: UNT Libraries Government Documents Department

Transition from quasi-elastic to deep-inelastic reactions

Description: Heavy ion induced transfer reactions are usually considered to fall into two categories. Quasi-elastic processes, on one hand, are characterized by small energy transfers, with one-nucleon transfer reactions being a typical example. These processes are dominant for grazing collisions, and are generally described within simple one-step DWBA calculations. Deep inelastic reactions, on the other hand, occur for more central collisions where the interaction time is longer and subsequently more energy and particles can be exchanged. Quasi-elastic collisions dominate transfer reactions induced by light heavy ions (e.g., /sup 16/O) at energies not too high above the barrier, while deep inelastic collisions are observed mainly in reactions induced by heavier projectiles (Kr, Xe). In this contribution, we discuss the transition between these two processes for the system /sup 48/Ti + /sup 208/Pb. /sup 48/Ti is located between light (/sup 16/O) and heavy (Kr) projectiles and should be well suited for a study of the interrelation between quasi- and deep-inelastic reactions. The experiments were performed with a 300 MeV /sup 48/Ti beam obtained from the Argonne National Laboratory superconducting linac. The outgoing particles were momentum analyzed in a split pole magnetic spectrograph and detected in the focal plane by a position sensitive ionization chamber. The specific energy loss, the magnetic rigidity and the total energy of the outgoing particles were measured enabling mass and Z-identification. The energy resolution was about 3 MeV, determined by the thickness of the /sup 208/Pb target, and thus excluded study of transfer reactions to discrete final states. Angular distributions were measured in the range theta/sub lab/ = 20/sup 0/ to 80/sup 0/ in steps of 5/sup 0/. 8 refs.
Date: January 1, 1986
Creator: Rehm, K.E.
Partner: UNT Libraries Government Documents Department

Nuclear research with heavy ions. Annual progress report, January 1, 1977--December 31, 1977

Description: The experimental research program consists of several interrelated parts: (1) Reactions of Very Heavy Ions with Complex Nuclei; (2) Studies of Compound Nucleus Reactions Induced by Heavy Ions; and (3) Recoil Studies of Heavy Ion Reactions. Using solid-state detector telescopes and gas-ionization detector telescopes we have studied the emission of /sup 1/H, /sup 2/H, /sup 3/H, /sup 4/He and heavy fragments from the reactions of 720 MeV /sup 86/Kr with /sup 197/Au. Coincidence measurements between light charged particles and a heavy fragment indicate that most of the observed /sup 4/He particles are evaporated by equilibrated Kr*-like and Au*-like excited products from deep inelastic reactions, but a significant number of preequilibrium /sup 4/He particles seem to be emitted in directions normal to the separating fragments. Studies of angular correlations between two heavy fragments provide strong evidence for sequential fission of the Au*-like reaction fragments, and the probability of this process has been estimated as a function of Q, the energy damping in the primary collision. Parallel studies of charged particle emission, fission, and evaporation residues in compound nucleus reactions map out the de-excitation characteristics of highly excited heavy nuclei as functions of E* and J. Results are presented for the compound nucleus /sup 194/Hg formed at matched excitation energies via different entrance channels.
Date: October 1, 1977
Creator: Kaplan, Morton
Partner: UNT Libraries Government Documents Department

Energy dissipation in heavy systems: the transition from quasi-elastic to deep-inelastic scattering

Description: The interaction of medium mass projectiles (A = 28 - 64) with /sup 208/Pb has been studied using a split-pole spectrograph which allows single mass and charge identification. The reaction process in all systems studied so far is dominated by quasi-elastic neutron transfer reactions, especially at incident energies in the vicinity of the Coulomb barrier. In addition to the quasi-elastic component deep inelastic contributions are present in all reaction channels. The good mass and charge separation allows to generate Wilczynski plots for individual channels; for the system /sup 48/Ti + /sup 208/Pb we observe that the transition between the quasi-elastic and deep-inelastic reactions occurs around Q = -(30 to 35) MeV.
Date: January 1, 1984
Creator: Rehm, K.E.; van den Berg, A.; Kolata, J.J.; Kovar, D.G.; Kutschera, W.; Rosner, G. et al.
Partner: UNT Libraries Government Documents Department

Optical models in the resolved resonance region

Description: Using modern time-of-flight facilities the resolved region can be extended upward to about 1 MeV for nuclei with A < 60 and for heavier nuclei near closed shells. A careful measurement both on and off resonances followed by an R-matrix analysis yields partial wave scattering functions which are easily energy averaged for comparison to those from an optical model. A comparison of average scattering functions of opposite parities can provide information on surface effects because the wave functions for different parities are out of phase at the surface. Thus, a unique supplement is made to the information that can be obtained from other types of measurements for both the bound region and higher energies. 16 refs., 9 figs., 1 tab.
Date: January 1, 1985
Creator: Johnson, C.H.
Partner: UNT Libraries Government Documents Department

Analysis of n + /sup 197/Au cross sections for E/sub n/ = 0. 01-20 MeV

Description: An analysis of n + /sup 197/Au reactions has been completed for incident neutron energies between 0.01 and 20 MeV. The analysis involves use of a deformed optical model to calculate neutron transmission coefficients, a giant-dipole-resonance model and experimental data to determine gamma-ray transmission coefficients, and Hauser-Feshbach statistical theory to calculate partial reaction cross sections. Particular emphasis was given to obtaining gamma-ray strength functions that are consistent with spectral measurements of gamma-ray emission between E/sub n/ = 0.2 and 20 MeV by Morgan and Newman, while at the same time requiring agreement with (n,..gamma..) and (n,xn) cross-section data. 16 references.
Date: September 9, 1984
Creator: Young, P.G. & Arthur, E.D.
Partner: UNT Libraries Government Documents Department

Nuclear scattering studies by the scattering of medium-energy electrons. Progress report, October 1, 1979-September 30, 1980. [Univ. of Massachusetts, Amherst, 10/1/79-9/30/80]

Description: Electron scattering experiments are in progress at the Bates Linear Accelerator in Middleton, Massachusetts. Both magnetic elastic and transverse inelastic scattering cross sections have been measured at 180/sup 0/ by the apparatus constructed and brought into operation in late 1977 by the University of Massachusetts. Coulomb contributions to the scattering have been measured at forward angles. Scattering from the ground-state magnetization distributions of /sup 13/C, /sup 15/N, and /sup 27/Al have been measured out to a momentum transfer of 3.2 fm/sup -1/. Only the M1 multipole enters for the /sup 13/C and /sup 15/N, whereas M1, M3, and M5 are present for /sup 27/Al. Measurements of the transverse form factors of the excited states of /sup 13/C have been completed. Information on M4 stretched-spin cases and on transverse excitations have been obtained for the first time. The study of particle-hole stretched spin (g/sub 9/2/f/sub 7/2//sup -1/) M8 excitations in /sup 54,56/Fe and /sup 58,60/Ni is continuing. Comparison with hadron excitation to these states yields information on the hadron-nucleus interaction. A search for M1 excitations in /sup 208/Pb at energies up to 26 MeV at beam energies of 30, 40, 50, 60, and 75 MeV has been completed in collaboration with Oak Ridge National Laboratory. A liquid-nitrogen cooled deuterium target cell is being constructed for use in a study of the electrodisintegration of the deuteron. An /sup 15/N gas target cell was constructed, and the measurement of inelastic excitations is nearly completed. 8 figures.
Date: October 1, 1980
Creator: Peterson, G.A.
Partner: UNT Libraries Government Documents Department

High energy collisions of nuclei: experiments

Description: Heavy-ion nuclear reactions with projectile energies up to 2.1 GeV/A are reviewed. The concept of ''rapidity'' is elucidated, and the reactions discussed are divided into sections dealing with target fragmentation, projectile fragmentation, and the intermediate region, with emphasis on the production of light nuclei in high-energy heavy-ion collisions. Target fragmentation experiments using nuclear emulsion and AgCl visual track detectors are also summarized. 18 figures. (RWR)
Date: September 1, 1977
Creator: Heckman, H.H.
Partner: UNT Libraries Government Documents Department

Emission of heavy charged particles in relativistic nucleus--nucleus collisions. [500 MeV, nuclear energy and angular distributions, cross section, tables]

Description: The energy and angular distributions of nuclei produced in interactions of 500 MeV/nucl /sup 40/Ar projectiles with an Au target were investigated. Nuclei with charge 3 < or = to Z < or = to 11 were observed. Single particle inclusive spectra were obtained at angles between 35 and 85/sup 0/, in the energy range 20 to 60 MeV/nucl. The spectra decrease monotonically with the increasing energy, angle, and charge. The distributions are consistent with an isotropically emitting source recoiling with an average velocity of aproximately 0.08 c in the beam direction. Thermal model fits to the data yield temperatures tau of about tau approximately 60 MeV. The low recoil velocity and high temperature are shown to be in conflict with energy and momentum conservation. Two nonthermal models of emission involving expansion or rotation are explored. Although neither of these models gives good quantitative fits to the data, they do much better than the thermal model if it is constrained to be energy and momentum conserving. The data for all energies, angles and species may be simply parameterized. When transformed into a recoiling source frame with ..beta../sub 0/ approximately equal to 0.08, all data points lie near (+-4x) a common curve, for which the invariant cross section, f identical with (1/p) (d/sup 2/ sigma/d..cap omega..dE), falls exponentially with increasing momentum, f varies as e/sup /sup -/p/p/sub c//, with a characteristic momentum p/sub c/ approximately equal to 340 MeV/c.
Date: December 1, 1977
Creator: Stevenson, J.D.
Partner: UNT Libraries Government Documents Department