Recent Articles

${}^{20}{Ne}$ -induced reactions with Cu and ${}^{197}{Au}$ at 8.6 and 12.6 MeV/nucleon

G. J. Mathews, J. B. Moulton, G. J. Wozniak, B. Cauvin, R. P. Schmitt, J. S. Sventek, and L. G. Moretto

Phys. Rev. C 25, 300 (1982) - Published 1 January, 1982

Show Abstract

Products from the reactions of 170- and 252-MeV ${}^{20}{Ne}$ with ${}^{nat}{Cu}$ and ${}^{197}{Au}$ have been studied. The charge and angular distributions of the $Z$ -identified fragments are discussed in terms of diffusion along the mass-asymmetry coordinate. This diffusion model has been generalized to include the effects of shape evolution, which is important for these deeply penetrating systems, and also the effect of $\frac{N}{Z}$ equilibration, which is important for highly asymmetric systems such as ${}^{20}{Ne}$ + ${}^{197}{Au}$ .

NUCLEAR REACTIONS ${}^{nat}{Cu}$ , ${}^{197}{Au}$ ( ${}^{20}{Ne}$ , $Z$ ), $E = 170 and 252$ MeV. Measured $σ (E, Z, θ)$ , for $6 \leq Z \leq 30$ . Theoretical interpretation based on a diffusion model.

Entrance channel effects by populating resonances in the ${}^{26}{Al}$ , ${}^{29}{Si}$ , and ${}^{30}{Si}$ systems

R. L. Parks, S. T. Thornton, K. R. Cordell, and C. -A. Wiedner

Phys. Rev. C 25, 313 (1982) - Published 1 January, 1982

Show Abstract

Excitation functions have been measured for the elastic, recoil, and alpha-particle exit channels for four reactions: ${}^{17}O$ + ${}^{12}C$ ( $E_{lab} = 30.0 - 57.0$ MeV), ${}^{16}O$ + ${}^{13}C$ ( $E_{lab} = 29.5 - 52.6$ MeV), ${}^{17}O$ + ${}^{13}C$ ( $E_{lab} = 30.0 - 57.0$ MeV), and ${}^{16}O$ + ${}^{10}B$ ( $E_{lab} = 42.4 - 60.1$ MeV). The alpha particles were detected at $θ_{lab} = 10 °$ while the elastic and recoil particles were detected at $θ_{lab} = 34 °$ . Statistical analyses of the data are used to search for correlated, nonstatistical structures in the excitation functions. The resonant properties of three compound nuclei ( ${}^{26}{Al}$ , ${}^{29, 30}{Si}$ ) are studied by comparing the excitation energies at which nonstatistical structures are seen when the nuclei are formed via different well matched (in terms of $J_{max}$ ) entrance channels. These resonancelike structures seen in the various entrance channels (for a given compound nucleus) are found to be uncorrelated in excitation energy, thereby implying a dependence upon the properties of the entrance channel. The lack of entrance channel correlations and the short lifetimes of the structures seen are viewed as evidence that the reaction may proceed through a quasimolecule, or that the compound nucleus itself is so highly excited and deformed that its formation is entrance channel dependent.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{17}O$ , ${}^{17}O$ ), ( ${}^{17}O$ , ${}^{12}C$ ), ( ${}^{17}O$ , $α$ ), $E = 30.0 - 57.0$ MeV; ${}^{13}C$ ( ${}^{16}O$ , ${}^{16}O$ ), ( ${}^{16}O$ , ${}^{13}C$ ), ( ${}^{16}O$ , $α$ ), $E = 29.5 - 52.6$ MeV; ${}^{13}C$ ( ${}^{17}O$ , ${}^{17}O$ ), ( ${}^{17}O$ , ${}^{13}C$ ), ( ${}^{17}O$ , $α$ ), $E = 30.0 - 57.0$ MeV; ${}^{10}B$ ( ${}^{16}O$ , ${}^{16}O$ ), ( ${}^{16}O$ , ${}^{10}B$ ), ( ${}^{16}O$ , $α$ ), $E = 42.4 - 60.1$ MeV. Measured $σ (E)$ at $θ_{lab} = 10 °$ for $α$ and $σ (E)$ at $θ_{lab} = 34 °$ for elastic and recoil. Natural ${}^{12}C$ target; enriched ${}^{13}C$ and ${}^{10}B$ targets. Resolution ∼100 keV for $α$ , 400-600 keV for elastic and recoil. Statistical and Hauser-Feshbach analyses. Entrance channel comparisons. Discussion of reaction mechanism.

Masses of ${}^{98}{Pd}$ , ${}^{99}{Pd}$ , and ${}^{100}{Pd}$

C. E. Thorn, W. F. Piel, Jr., M. J. LeVine, P. D. Bond, and A. Gallman

Phys. Rev. C 25, 331 (1982) - Published 1 January, 1982

Show Abstract

The $Q$ values of the reactions ${}^{96}{Ru}$ ( ${}^{16}O$ , ${}^{14 - 12}C$ ) ${}^{98 - 100}{Pd}$ have been simultaneously measured using a quadrupole-dipole-dipole-dipole magnetic spectrometer. The result for the ( ${}^{16}O$ , ${}^{14}C$ ) reaction is $Q = - 12.529 \pm 0.020$ MeV, from which we deduce the first measured mass excess of ${}^{98}{Pd}$ : -81.303±0.022 MeV. The $Q$ value for the ( ${}^{16}O$ , ${}^{13}C$ ) reaction is determined to be -11.723±0.020 MeV, from which we obtain -82.214±0.022 MeV for the mass excess of ${}^{99}{Pd}$ . This value is the first direct measurement of the mass of ${}^{99}{Pd}$ , and disagrees with a previously tabulated value. For the ( ${}^{16}O$ , ${}^{12}C$ ) reaction, $Q = - 5.599 \pm 0.026$ MeV, which leads to a mass excess for ${}^{100}{Pd}$ of -85.213±0.027 MeV, in agreement with a previous measurement using light ions. A mass excess of -87.138±0.022 MeV for ${}^{106}{Cd}$ , measured with the ${}^{104}{Pd}$ ( ${}^{16}O$ , ${}^{14}C$ ) reaction, is also in excellent agreement with a tabulated value.

NUCLEAR REACTIONS ${}^{16}O$ + ${}^{96}{Ru}$ , $E = 70$ MeV; measured $E_{{}^{14}C}$ , $E_{{}^{13}C}$ , $E_{{}^{12}C}$ ; ${}^{98}{Pd}$ , ${}^{99}{Pd}$ , ${}^{100}{Pd}$ deduced level, $Q$ , masses; QDDD magnetic spectrometer.

Influence of the impact parameter on element distributions in dissipative heavy-ion collisions

H. J. Wollersheim, W. W. Wilcke, J. R. Birkelund, and J. R. Huizenga

Phys. Rev. C 25, 338 (1982) - Published 1 January, 1982

Show Abstract

The ${}^{209}{Bi}$ + ${}^{136}{Xe}$ reaction at laboratory bombarding energies of 940, 1130, and 1422 MeV is interpreted on the basis of a phenomenological classical model and a diffusion model for damped collisions. Initial angular momenta, interaction times, and charge diffusion coefficients are deduced with the above models from experimental data reported previously. The bombarding energy dependence of the model parameters and the effect of deformation on the dinuclear system in the exit channel are discussed. An analytical relation is suggested between the variance ${σ_{Z}}^{2}$ of the element distribution and the ratio $\frac{E}{l_{g}}$ , where $E$ is the measured final total kinetic energy and $l_{g}$ is the grazing orbital angular momentum. This semiempirical formula is applied to sixteen heavy-ion systems at bombarding energies well above the Coulomb barrier. In a plot of $\ln {σ_{Z}}^{2}$ versus $\frac{E}{l_{g}}$ all the experimental data fall on parallel lines with displacements that are reasonably well correlated with $\frac{E_{0}}{l_{g}}$ , where $E_{0}$ is the bombarding energy in the c.m. system. In a model-dependent explanation of this empirical relation, evidence is found that the variance of the element distributions ${σ_{Z}}^{2}$ is determined by the initial relative angular momentum $\frac{l}{l_{g}}$ .

NUCLEAR REACTIONS ${}^{209}{Bi}$ ( ${}^{136}{Xe}$ ,HI), $E_{lab} = 940, 1130, and 1422$ MeV; deduced initial angular momentum, interaction time and charge diffusion coefficient; strongly damped reaction; systematics of heavyion reaction data.

Production of ${}^{6}{He}$ , ${}^{6}{Li}$ , ${}^{7}{Li}$ , and ${}^{7}{Be}$ in the $α + a$ reaction between 60—160 MeV

B. G. Glagola, V. E. Viola, Jr., H. Breuer, N. S. Chant, A. Nadasen, P. G. Roos, Sam M. Austin, and G. J. Mathews

Phys. Rev. C 25, 34 (1982) - Published 1 January, 1982

Show Abstract

Cross sections for the production of ${}^{6}{He}$ , ${}^{6}{Li}$ , ${}^{7}{Li}$ , and ${}^{7}{Be}$ produced in the $α + α$ reaction have been measured over the energy range 60—160 MeV. Detailed angular distributions are presented for exit channels leading to ${}^{7}{Li}$ , ${}^{7}{Be}$ , and ${}^{6}{Li}$ (g.s.), along with cross sections for the three-body exit channels leading to the production of ${}^{6}{He}$ and ${}^{6}{Li}$ . The astrophysical significance of the $α + α$ reaction is discussed with particular emphasis on the production of ${}^{7}{Li}$ in the interaction of galactic cosmic rays with the interstellar medium. In addition, two-nucleon-transfer distorted-wave Born approximation calculations are presented in an attempt to understand the reaction mechanism operating in the $α (α, d) {}^{6}{Li} (g . s .)$ reaction.

NUCLEAR REACTIONS ${}^{4}{He}$ ( ${}^{4}{He}$ ,HI), HI= ${}^{6}{He}$ , ${}^{6}{Li}$ , ${}^{7}{Li}$ , and ${}^{7}{Be}$ ; $E = 60 - 160$ MeV; measured $\frac{d^{2} σ}{d Ω dE}$ and $σ (E)$ ; astrophysical relevance discussed; DWBA calculations for ${}^{4}{He}$ ( ${}^{4}{He}$ , $d$ ) ${}^{6}{Li}$ .

Excited states in ${}^{68}{Ge}$ and ${}^{69}{Ge}$ studied by the ${}^{64}{Zn}$ ( ${}^{7}{Li}$ , $pxn γ$ ) reaction

T. Paradellis and C. A. Kalfas

Phys. Rev. C 25, 350 (1982) - Published 1 January, 1982

Show Abstract

Excited states in ${}^{68}{Ge}$ and ${}^{69}{Ge}$ populated in the ${}^{64}{Zn}$ + ${}^{7}{Li}$ reaction at 18 MeV bombarding energy are studied. Angular distribution and centroid shift measurements are used to determine spin and mean lives in these nuclei. The first $2^{+}$ state in ${}^{68}{Ge}$ has been remeasured to have a mean life of (2.6 ± 0.3) ps. In ${}^{69}{Ge}$ discrepancies among different published works are discussed. The experimental evidences are in favor of description of the positive parity states in ${}^{69}{Ge}$ , where a $g_{\frac{9}{2}}$ neutron is coupled to a ${}^{68}{Ge}$ even-even core.

NUCLEAR REACTIONS ${}^{64}{Zn}$ ( ${}^{7}{Li}$ , $pxn$ ) ${}^{68}{Ge}$ , ${}^{69}{Ge}$ , $E = 15 - 18$ MeV. Measured $I_{γ} (θ)$ , $E_{γ} (θ)$ . Doppler attenuation centroid shift. ${}^{68}{Ge}$ , ${}^{69}{Ge}$ deduced $J^{π}$ , $δ$ , $τ$ . Enriched target, Ge(Li) detector.

Fission fragment angular momentum: Ratios of independent yields of isomers of ${}^{95}{Nb}$ and ${}^{132}I$ in thermal-neutron-induced fission of ${}^{233}U$

T. Datta, S. P. Dange, A. G. C. Nair, Satya Prakash, and M. V. Ramaniah

Phys. Rev. C 25, 358 (1982) - Published 1 January, 1982

Show Abstract

Independent isomeric yield ratios of the fission products ${}^{95}{Nb}$ and ${}^{132}I$ in thermal-neutron-induced fission of ${}^{233}U$ have been determined radiochemically. The determined ratios are 0.248 ± 0.029 and 0.268 ± 0.084 for the isomers of ${}^{95}{Nb}$ and of ${}^{132}I$ , respectively. On the basis of these yield ratios the average angular momenta of the primary fragments, respective of the fission products ${}^{95}{Nb}$ and ${}^{132}I$ , have been estimated using the statistical model formalism. The estimated values are ${6.35}_{- 0.95}^{+ 1.25} ℏ$ and $5.7 \pm 1.2 ℏ$ for ${}^{95}{Nb}$ and ${}^{132}I$ , respectively. These data along with other literature data show that fragment angular momenta decrease as proton number deviates from spherical magic shell 50 for given neutron number. Besides, fragment angular momenta do not correlate with prompt neutron number.

NUCLEAR REACTIONS, FISSION ${}^{233}U$ ( $n_{th}$ , $f$ ); measured independent isomeric yield ratios of ${}^{95}{Nb}$ and ${}^{132}I$ ; estimated fragment angular momenta using statistical model, effect of deformation, prompt neutron number.

Monte Carlo calculation of the deexcitation of fission fragments in the spontaneous fission of ${}^{252}{Cf}$

M. Kildir and N. K. Aras

Phys. Rev. C 25, 365 (1982) - Published 1 January, 1982

Show Abstract

The consequences of the evaporation of prompt neutrons and $γ$ rays from primary fission fragments in the spontaneous fission of ${}^{252}{Cf}$ have been examined by a Monte Carlo method. A semiempirical mass equation and experimental values of total kinetic energies are used to obtain the sum of excitation energies of complementary fragments. The division of this energy between complementary fragments is determined by the two-spheroid model for the scission configuration. The prompt neutron multiplicity distribution gives a value of 3.68 for the average number of prompt neutrons in ${}^{252}{Cf}$ (sf). Calculated values of the average number of prompt neutrons as a function of fragments mass are in good agreement with the experimental values. Calculated results for the charge dependence of total $γ$ -ray energies show an odd-even effect, whereas no such effect is apparent in the charge dependence of the average number of neutrons. Mass and charge distributions of secondary fission fragments are also well reproduced in the calculations.

NUCLEAR REACTIONS, FISSION ${}^{252}{Cf}$ (sf); calculated prompt neutrons and $γ$ rays. Pairing effect on $γ$ -ray energy.

Elastic $p - p$ scattering at 796 MeV in the Coulomb-nuclear interference region

F. Irom, G. J. Igo, J. B. McClelland, and C. A. Whitten, Jr.

Phys. Rev. C 25, 373 (1982) - Published 1 January, 1982

Show Abstract

By measuring the energy of recoil particles, the following data have been obtained at an incident proton energy of 796 MeV: (1) the differential cross section for proton-proton ( $p - p$ ) elastic scattering at laboratory angles between 1.37° and 6.40°, and (2) the analyzing power for $p - p$ elastic scattering at laboratory angles between 3.13° and 6.40°. Analyses of these data have determined certain parameters characterizing the nuclear amplitude for $p - p$ elastic scattering. The ratio $ρ$ of the real to the imaginary parts of the forward $p - p$ spin independent amplitude was found to be + 0.005±0.04. The ratio $R$ of the summed moduli squared of the forward $p - p$ double spin flip scattering amplitudes to the modulus squared of the forward $p - p$ spin independent amplitude was found to be 0.16±0.03. The real and imaginary parts of the $p - p$ spin orbit scattering amplitude divided by $sin θ$ were found to be 0.72±0.05 and 0.18±0.11 fm, respectively. These values are compared with results of recent phase-shift analyses and forward dispersion relation calculations.

NUCLEAR REACTIONS ${}^{1}H$ ( $p$ , $p$ ) ${}^{1}H$ , $E = 796$ MeV, measured $σ (t)$ and $A_{y} (t)$ .

Coulomb effects in nuclear collisions

M. Bawin and J. Cugnon

Phys. Rev. C 25, 387 (1982) - Published 1 January, 1982

Show Abstract

We compare the analytic approximation to the Coulomb phase space factor recently given by Gyulassy and Kauffmann to the expression obtained from an exact solution of the Klein-Gordon equation. We find that while the agreement is excellent for pions in field of small $Z$ (Ne) nuclei, a difference in magnitude of order $10^{2}$ may occur for low energy pions in high $Z$ (Pb) fields, thus suggesting that an exact solution to the Klein-Gordon equation may be useful in the analysis of Coulomb effects in nuclear collisions of heavy elements.

NUCLEAR REACTIONS Coulomb final state interaction in pion production. Exact solution of Klein-Gordon equation. Comparison with simple approximation.

${}^{4}{He}$ ( $p$ , $2 p$ ) ${}^{3}H$ reaction at intermediate energies

W. T. H. van Oers, B. T. Murdoch, B. K. S. Koene, D. K. Hasell, R. Abegg, D. J. Margaziotis, M. B. Epstein, G. A. Moss, L. G. Greeniaus, J. M. Greben, J. M. Cameron, J. G. Rogers, and A. W. Stetz

Phys. Rev. C 25, 390 (1982) - Published 1 January, 1982

Show Abstract

The ${}^{4}{He}$ ( $p$ , $2 p$ ) ${}^{3}H$ reaction has been studied at 250, 350, and 500 MeV using coplanar symmetric and asymmetric geometries. The data are presented as energy-sharing spectra, coplanar symmetric angular distributions, and quasifree angular distributions. A comparison with distorted wave impulse approximation calculations indicates reasonable agreement for small recoil momenta ( $q ≲ 150$ MeV/c). For larger recoil momenta, the distorted-wave impulse approximation calculations increasingly underestimate the data. The discrepancies are substantially reduced by inclusion of a spin-orbit term in the optical potential used to generate the distorted waves. Improvements of the single particle wave function for the struck nucleon influence the calculations to a lesser degree. The remaining discrepancies at large recoil momenta may, in part, be ascribed to multiple scattering effects and exchange processes not included in the standard distorted-wave impulse approximation.

NUCLEAR REACTIONS ${}^{4}{He}$ ( $p$ , $2 p$ ) ${}^{3}H$ ; measured $\frac{d^{3} σ}{(d Ω_{3} d Ω_{1} d T_{3})}$ , 250, 350, 500 MeV, energy sharing spectra, coplanar symmetric angular distributions, quasifree angular distributions; comparison with DWIA calculations.

Neutron-proton decomposition of transition matrix elements from a comparison of 800 MeV proton scattering with electromagnetic methods

M. M. Gazzaly, N. M. Hintz, G. S. Kyle, R. K. Owen, G. W. Hoffmann, M. Barlett, and G. Blanpied

Phys. Rev. C 25, 408 (1982) - Published 1 January, 1982

Show Abstract

Differential cross sections for inelastic proton scattering at 800 MeV have been measured for a number of low-lying states in ${}^{90}{Zr}$ , ${}^{120}{Sn}$ , ${}^{144}{Sm}$ , and ${}^{208}{Pb}$ . The data from this and earlier experiments on ${}^{40}{Ca}$ and ${}^{58}{Ni}$ were analyzed with a collective vibrational model to obtain separate neutron and proton deformation lengths, making use of electromagnetic measurements. Ratios of neutron to proton transition matrix elements are calculated. These ratios are generally less than $\frac{N}{Z}$ for the open proton shell nuclei and greater for the open neutron shell nuclei.

NUCLEAR REACTIONS ${}^{90}{Zr}$ , ${}^{120}{Sn}$ , ${}^{144}{Sm}$ , ${}^{208}{Pb}$ ( $p$ , $p^{'}$ ), $E = 800$ MeV; measured $σ (θ)$ , $θ_{lab} = 5 ° - 20 °$ . Optical model and DWBA collective model analysis. Deformation lengths and neutron to proton matrix element ratios are extracted for the above and ${}^{40}{Ca}$ , ${}^{58}{Ni}$ .

Elastic and inelastic scattering of 0.8 GeV protons from ${}^{24}{Mg}$ and ${}^{26}{Mg}$

G. S. Blanpied, N. M. Hintz, G. S. Kyle, M. A. Franey, S. J. Seestrom-Morris, R. K. Owen, J. W. Palm, D. Dehnhard, M. L. Barlett, C. J. Harvey, G. W. Hoffmann, J. A. McGill, R. P. Liljestrand, and L. Ray

Phys. Rev. C 25, 422 (1982) - Published 1 January, 1982

Show Abstract

Angular distributions for the elastic and inelastic scattering of 0.8 GeV protons from ${}^{24}{Mg}$ and ${}^{26}{Mg}$ are presented. Cross sections for protons exciting states of energy up to about 10 MeV are measured using a high resolution spectrometer. Coupled channels analyses of scattering data to the $0^{+}$ , $2^{+}$ , $4^{+}$ , and $6^{+}$ states in the ground state rotational band, the $2^{+}$ , $3^{+}$ , $4^{+}$ , and $6^{+}$ states in the $γ$ -vibrational band, the $0^{+}$ , $2^{+}$ , and $4^{+}$ states in the $β$ -vibrational band, and the $3^{-}$ and $5^{-}$ members of the $K^{π} = 0^{-} and 3^{-}$ vibrational bands in ${}^{24}{Mg}$ are presented. Also reported are coupled channels analyses of the experimental angular distributions in ${}^{26}{Mg}$ for the $0^{+}$ , $2^{+}$ , and $4^{+}$ states in the ground state band, the possible $2^{+}$ , $3^{+}$ , and $4^{+}$ , $γ$ -band members, and several $3^{-}$ members of $K^{π} = 0^{-} and 3^{-}$ bands. The data for the $3^{-}$ states in both ${}^{24}{Mg}$ and ${}^{26}{Mg}$ differ both in shape and angular positions of the maxima and minima. Coupled channels analyses are able to account for these differences in the $3^{-}$ experimental cross sections by selecting $K^{π} = 0^{-} or 3^{-}$ . This is believed to be the first observation of " $K$ dependence" for $l = 3$ excitations in inelastic scattering by $s - d$ shell nuclei. Distorted wave Born approximation analyses of the other states in ${}^{26}{Mg}$ excited by $l$ transfers from 2 to 4 are also described. Several new assignments of $J^{π}$ for excited states in ${}^{26}{Mg}$ are proposed based upon the distinctive $l$ transfer dependence found in the positions of the first maximum and in the general shapes of the angular distributions. Multipole moments extracted from the deformed optical potentials are related to those of the matter distributions by Satchler's theorem. These are compared to multipole moments obtained from analyses of hadronic scattering data, as well as with the moments of the charge distributions determined by electromagnetic measurements.

NUCLEAR REACTIONS ${}^{24, 26}{Mg}$ ( $p$ , $p^{'}$ ), $E = 0.8$ GeV, measured $σ (θ)$ , enriched targets; resolution ≥80 keV, $θ_{c . m .} = 5.49 ° to 31.66 °$ , $Δ θ = 0.1 °$ . Optical model potential, DWBA analysis, coupled channels analysis, symmetric and asymmetric rotational model, coupling parameters, multipole moments, assigned $J^{π}$ .

${}^{3}{He}$ ( $π^{-}$ , $π^{0}$ ) reaction at $T_{π} = 200$ MeV

M. D. Cooper, H. W. Baer, J. D. Bowman, F. H. Cverna, R. H. Heffner, C. M. Hoffman, N. S. P. King, J. Piffaretti, J. Alster, A. Doron, S. Gilad, M. A. Moinester, P. R. Bevington, and E. Winklemann

Phys. Rev. C 25, 438 (1982) - Published 1 January, 1982

Show Abstract

Energy and angle differential cross sections for the ${}^{3}{He}$ ( $π^{-}$ , $π^{0}$ ) reaction at $T_{π} = 200$ MeV have been measured. Angular distributions for the isobaric analog state and the energy integrated continuum have been obtained from 0° to 90°. The excitation of the analog state seems to be best represented by Glauber model calculations with nuclear wave functions suitable to explain electron scattering, but all model calculations underestimate the forward angles by 1.5 standard errors. The continuum angular distribution has the same shape as the free $p (π^{-}, π^{0}) n$ reaction except at forward angles, where the cross section is suppressed by Pauli blocking of the final state. The total isobaric analog state cross section is 6.29±0.94 mb and the total charge exchange cross section from 0° to 90° is 28.4±3.8 mb. The latter is one-half the plane wave impulse approximation value.

NUCLEAR REACTIONS ${}^{3}{He}$ ( $π^{-}$ , $π^{0}$ ); $T_{π^{-}} = 200$ MeV; measured $σ (θ)$ ; $θ = 0 ° - 90 °$ ; analog state; continuum; compare to theory; deduced effective number of nucleons and Pauli blocking effects.

Unified theory of rearrangement scattering

J. M. Greben

Phys. Rev. C 25, 446 (1982) - Published 1 January, 1982

Show Abstract

We present a unified microscopic theory of rearrangement scattering which satisfies the Pauli principle. The equations for the transition amplitudes and wave functions are reduced to effective two-body equations with the complexity put into the distortion potentials and the transition potentials. The central theme in the development of this theory is the importance of elastic scattering in the initial and the final channel, although this is not a prerequisite for its validity as the theory is exact. The elastic degrees of freedom are absorbed into the distorted waves using projection techniques in combination with the Faddeev formulation. The resulting transition amplitude can be expanded in the transition potential, leading to a modified coupled channel series. The transition potential, which has a constructive nature (i.e., no counter terms), can also be expanded. We provide arguments for the convergence of both expansions. Various contributions to the transition potential are discussed, and we put special emphasis on a rescattering term which has not been considered before in the context of coupled channel equations. Various inconsistencies which may hamper standard coupled channel calculations are discussed as well.

NUCLEAR REACTIONS Microscopic theory of rearrangement scattering. DWBA. Coupled channel effects. Rescattering contribution. Two-nucleon mechanism. ( $p$ , $d$ ) reaction.

Properties of energy-independent nuclear optical potentials

J. T. Londergan and Gerald A. Miller

Phys. Rev. C 25, 46 (1982) - Published 1 January, 1982

Show Abstract

For separable, coupled-channel model interactions we show how to construct energy-independent optical potentials, $\bar{U}$ . The elastic phase shifts and nuclear wave functions obtained from $\bar{U}$ are identical at all energies with those of the conventional energy-dependent optical potential $U (E)$ . Whenever there is strong absorption or a compound resonance $\bar{U}$ has an extremely rapid variation with momentum.

NUCLEAR REACTIONS Energy-independent optical potentials. Separable interaction model; compare momentum dependence of conventional and energy-independent optical potentials; compare with phase-shift-equivalent potentials.

Production of Kr and Xe isotopes by interaction of ${}^{232}{Th}$ with 0.15-24 GeV protons

H. Sauvageon, S. Regnier, and G. N. Simonoff

Phys. Rev. C 25, 466 (1982) - Published 1 January, 1982

Show Abstract

Cross sections and thick-target recoil properties of several Kr and Xe isotopes formed in the interaction of ${}^{232}{Th}$ with 0.15-24 GeV protons have been determined in order to study their variations with mass product and incident energy. High sensitivity mass spectrometry has been used to measure noble gas isotopic composition and concentration. The recoil technique, combined with a mathematical formalism based on the two-step model, permits the determination of some characteristics of the nuclear reactions; i.e., the range $R$ , the mean kinetic energy $〈 T 〉$ , the observed products and the excitation energy $E^{*}$ , and the residual nucleus after intranuclear cascade. The results are discussed in terms of fission and deep spallation mechanism. Fission contributes noticeably to the formation of neutron-excess products at all incident energies, while deep spallation concerns the most neutron-deficient isotopes at energies beyond 1 GeV. This last mechanism is described in terms of coherent interaction between incident protons and target nucleus.

NUCLEAR REACTIONS Measured $σ$ , $2 W (F + B)$ and $\frac{F}{B}$ of various Kr and Xe nuclides formed in interaction of ${}^{232}{Th}$ with 0.15-24 GeV protons.

Target- $A$ dependence of the angular distribution of Sc fragments emitted in 400 GeV proton interactions

J. S. Stewart and N. T. Porile

Phys. Rev. C 25, 478 (1982) - Published 1 January, 1982

Show Abstract

The angular distribution of Sc fragments emitted in the interaction of 400 GeV protons with Ag, La, Lu, and Au has been measured. The distribution for Ag is forward peaked, while that for Lu and Au is sideward peaked, with La being an intermediate case. The implications of this novel transition for the reaction mechanism are considered.

NUCLEAR REACTIONS Ag, La, Lu, $Au (p, x) {}^{44}{Sc}^{m}$ , ${}^{47, 48}{Sc}$ , $T_{p} = 400$ GeV; measured $\frac{d σ}{d Ω}$ .

Separable potential analysis of coupled $N N - N Δ$ scattering

B. J. VerWest

Phys. Rev. C 25, 482 (1982) - Published 1 January, 1982

Show Abstract

A simple coupled channel separable potential model is used to fit the $J^{p} = 2^{+} and 3^{-}$ $NN$ amplitudes. Analytic structure of the resulting amplitudes is studied with emphasis on the location of poles which may represent dibaryon resonances. The study shows that there exists a wide range of potential models which describe the observed rapid energy dependence in the amplitudes in terms of threshold effects with an absence of resonance poles.

NUCLEAR REACTIONS $NN \leftrightarrow N Δ$ . Scattering theory, $N N - N Δ$ coupled separable potentials, ${}^{1}D_{2}$ and ${}^{3}F_{3}$ amplitudes calculated, pseudoresonance threshold behavior.

Model for the spin, isospin, and energy dependence of pion-nucleus annihilation

K. -B. Yoo and R. H. Landau

Phys. Rev. C 25, 489 (1982) - Published 1 January, 1982

Show Abstract

The pion-nucleus optical potential is extended to include terms describing the effect of pion annihilation on $pn$ and $\frac{pp}{nn}$ pairs with accompanying possibility of spin flip. An isobar model is generalized and fit to pion production data in all charge channels, and then the strengths for different spin-isospin absorption channels are projected out as a function of energy.

NUCLEAR REACTIONS Pion annihilation, absorption, function of energy, isospin, spin, optical potential.

Select page:

Physical Review C

Recent Articles

Filter

Recent Issues

${}^{20}{Ne}$ -induced reactions with Cu and ${}^{197}{Au}$ at 8.6 and 12.6 MeV/nucleon

Entrance channel effects by populating resonances in the ${}^{26}{Al}$ , ${}^{29}{Si}$ , and ${}^{30}{Si}$ systems

Masses of ${}^{98}{Pd}$ , ${}^{99}{Pd}$ , and ${}^{100}{Pd}$

Influence of the impact parameter on element distributions in dissipative heavy-ion collisions

Production of ${}^{6}{He}$ , ${}^{6}{Li}$ , ${}^{7}{Li}$ , and ${}^{7}{Be}$ in the $α + a$ reaction between 60—160 MeV

Excited states in ${}^{68}{Ge}$ and ${}^{69}{Ge}$ studied by the ${}^{64}{Zn}$ ( ${}^{7}{Li}$ , $pxn γ$ ) reaction

Fission fragment angular momentum: Ratios of independent yields of isomers of ${}^{95}{Nb}$ and ${}^{132}I$ in thermal-neutron-induced fission of ${}^{233}U$

Monte Carlo calculation of the deexcitation of fission fragments in the spontaneous fission of ${}^{252}{Cf}$

Elastic $p - p$ scattering at 796 MeV in the Coulomb-nuclear interference region

Coulomb effects in nuclear collisions

${}^{4}{He}$ ( $p$ , $2 p$ ) ${}^{3}H$ reaction at intermediate energies

Neutron-proton decomposition of transition matrix elements from a comparison of 800 MeV proton scattering with electromagnetic methods

Elastic and inelastic scattering of 0.8 GeV protons from ${}^{24}{Mg}$ and ${}^{26}{Mg}$

${}^{3}{He}$ ( $π^{-}$ , $π^{0}$ ) reaction at $T_{π} = 200$ MeV

Unified theory of rearrangement scattering

Properties of energy-independent nuclear optical potentials

Production of Kr and Xe isotopes by interaction of ${}^{232}{Th}$ with 0.15-24 GeV protons

Target- $A$ dependence of the angular distribution of Sc fragments emitted in 400 GeV proton interactions

Separable potential analysis of coupled $N N - N Δ$ scattering

Model for the spin, isospin, and energy dependence of pion-nucleus annihilation

Filter

Recent Issues

Filter

Article Lookup

Enter a citation