Recent Articles

Mechanisms for composite particle production in nuclear reactions using ( $α, α^{'} x$ ) reactions up to 40 MeV/nucleon

H. Machner, U. Bechstedt, A. Djaloeis, and P. Jahn

Phys. Rev. C 26, 411 (1982) - Published 1 August, 1982

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Spectra of $α$ particles from 90, 120, and 160 MeV $α$ -induced reactions on ${}^{54}{Fe}$ have been measured and, together with data taken at 59 MeV, were analyzed in terms of the exciton coalescence model. Multiple-particle emission was found to be important in reproducing the shapes of the angle integrated spectra. Deduced radii $P_{0}$ of coalescence spheres in momentum space are consistent with the assumption that $P_{0}$ is constant.

NUCLEAR REACTIONS ${}^{54}{Fe} (α, α^{'} x)$ , $E = 59, 90, 120, 160$ MeV; measured $σ (ε, ϑ)$ , $σ (ε)$ ; exciton coalescence model analysis, thermodynamics of light nuclei production.

High-spin states in ${}^{60}{Cu}$

Tsan Ung Chan, M. Agard, J. F. Bruandet, B. Chambon, A. Dauchy, D. Drain, A. Giorni, F. Glasser, and C. Morand

Phys. Rev. C 26, 424 (1982) - Published 1 August, 1982

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The ${}^{60}{Cu}$ nucleus has been studied via the ${}^{58}{Ni} (α, pn γ)$ reaction using different techniques of in-beam $γ$ spectroscopy. As in the other odd-odd Cu isotopes, the $g_{\frac{9}{2}}$ shell plays an important role for the explanation of observed high-spin states. Some of these (particularly $6^{-}$ and $9^{+}$ states) could be interpreted as two-nucleon states in the framework of a crude shell model.

NUCLEAR REACTIONS ${}^{58}{Ni} (α, pn γ)$ , $E = 24 - 40$ MeV; measured $E_{γ}$ , $I_{γ} (θ)$ , $γ - γ$ coincidence lifetimes by DSAM; ${}^{60}{Cu}$ deduced high-spin levels, $J$ , $π$ .

${}^{180}{Ta}^{g, m}$ production cross sections from the ${}^{180}{Hf} (p, n)$ reaction

Eric B. Norman, Timothy R. Renner, and Patrick J. Grant

Phys. Rev. C 26, 435 (1982) - Published 1 August, 1982

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Cross sections have been determined for the production of the $J^{π} = 1^{+}$ ${}^{180}{Ta}^{g}$ from the ${}^{180}{Hf} (p, n)$ reaction from measurements of $γ$ rays emitted following the electron capture and $β$ decay of this 8.1-h state. Total ${}^{180}{Ta}$ production cross sections were determined from measurements of the thick-target ( $p, n$ ) yield. Upper limits on the cross sections for the production of the long-lived $J^{π} = 9^{-}$ ${}^{180}{Ta}^{m}$ were obtained by subtracting the ${}^{180}{Ta}^{g}$ cross sections from the total ( $p, n$ ) cross sections. These measurements are compared with the results of a statistical-model evaporation calculation.

NUCLEAR REACTIONS ${}^{180}{Hf} (p, n)$ , $E_{p} = 6.5 - 9.0$ MeV; measured total ( $p, n$ ) cross section, ${}^{180}{Ta}^{g}$ cross section; deduced ${}^{180}{Ta}^{m}$ cross section; statistical model calculation. Enriched target. Ge(Li) detector. Neutron detector.

${}^{74}{Ge} (p, α) {}^{71}{Ga}$ reaction at 36.25 MeV.

F. Pellegrini, G. Calvelli, D. Trivisonno, and P. Guazzoni

Phys. Rev. C 26, 441 (1982) - Published 1 August, 1982

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The ${}^{74}{Ge} (p, α) {}^{71}{Ga}$ reaction has been studied at 36.25 MeV bombarding energy. Angular distributions of alpha particles were recorded and analyzed with distorted-wave Born approximation theory and a totally microscopic form factor for the three-particle transfers. Theoretical calculations in a restricted shell-model space using a modified surface $δ$ interaction reproduce fairly well the ${}^{71}{Ga}$ excitation energies and the observed strengths in ( $d$ , ${}^{3}{He}$ ) and ( $p, α$ ) spectra, with the exception of the ( $p, α$ ) ground state transition. This disagreement confirms the anomalies observed by ( $d$ , ${}^{3}{He}$ ) reactions, in the occupation numbers $Z = 32$ and between $N = 40 and 42$ , which can be related to changes in the nuclear shape.

NUCLEAR REACTIONS, NUCLEAR STRUCTURE ${}^{74}{Ge} (p, α) {}^{71}{Ga}$ , $E = 36.25$ MeV, measured $σ (E_{x}, θ)$ ; enriched target; DWBA analysis. Calculated ${}^{71}{Ga}$ energy levels, ${}^{72}{Ge} (d, {}^{3}{He}) {}^{71}{Ga}$ and ${}^{74}{Ge} (p, α) {}^{71}{Ga}$ spectroscopic strengths.

Photoproton decay of the ${}^{45}{Sc}$ giant dipole resonance

D. Ryckbosch, E. Van Camp, R. Van de Vyver, E. Kerkhove, P. Van Otten, P. Berkvens, and H. Ferdinande

Phys. Rev. C 26, 448 (1982) - Published 1 August, 1982

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The absolute ( $γ, p_{0}$ ) differential cross sections for ${}^{45}{Sc}$ were measured at bremsstrahlung end point energies between 17 and 25 MeV. Using an artificially constructed pseudomonoenergetic photon spectrum, absolute cross sections for various semidirect photoproton reaction channels were also determined. The general structure in the total ( $γ, p$ ) cross section is discussed in terms of isospin and deformation effects. The direct, preequilibrium and equilibrium contributions to the photoproton decay of the giant dipole resonance equal about 35, 20, and 45%, respectively, of the total energy-integrated ( $γ, p$ ) cross section. Comparison is made with the predictions of the exciton model.

NUCLEAR REACTIONS ${}^{45}{Sc} (γ, p)$ , $E = 15.6 - 25$ MeV, $θ = 37 ° - 143 °$ ; measured $σ (E; θ)$ absolutely. Deduced $σ (E; p_{i})$ , $σ (E)$ , direct-semidirect cross section, isospin splitting, preequilibrium decay. Natural target.

$γ$ decay of states in ${}^{47}{Cr}$

G. Hardie, S. A. Gronemeyer, L. Meyer-Schützmeister, and A. J. Elwyn

Phys. Rev. C 26, 456 (1982) - Published 1 August, 1982

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States in ${}^{47}{Cr}$ were studied using the ${}^{46}{Ti} ({}^{3}{He}, 2 n) {}^{47}{Cr}$ reaction with 22-MeV ${}^{3}{He}$ ions and the ${}^{40}{Ca} ({}^{12}C, α n) {}^{47}{Cr}$ reaction with 38-MeV ${}^{12}C$ ions. Prompt and delayed $γ - γ$ coincidence studies were performed. The following decay scheme was established (energies in keV): ${\frac{15}{2}}^{-} \underset{1322.3}{\to} {\frac{11}{2}}^{-} \underset{1158.3}{\to} {\frac{7}{2}}^{-} \underset{75.4}{\to} {\frac{5}{2}}^{-} \underset{99.3}{\to} {\frac{3}{2}}^{-} (g . s .)$ (g.s.). In addition, the ${\frac{3}{2}}^{+}$ state was determined to have an excitation energy of 471.5 keV and was found to decay to the ${\frac{5}{2}}^{-}$ state. Since ${}^{47}{Cr}$ has $T_{z} = \frac{1}{2}$ and is the mirror of the well-known ${}^{47}V$ nucleus, Coulomb displacement energies were deduced. The variation of Coulomb displacement energy with mass number is discussed for $f_{\frac{7}{2}}$ shell nuclei. In addition, we used the measured energies for the first ${\frac{3}{2}}^{+}$ states in $T = \frac{1}{2}$ mirror pairs of $f_{\frac{7}{2}}$ shell nuclei to determine the average Coulomb interaction energy between a $d_{\frac{3}{2}}$ hole and an $f_{\frac{7}{2}}$ particle, and found an increase in magnitude with increasing mass number.

NUCLEAR REACTIONS ${}^{46}{Ti} ({}^{3}{He}, 2 n) {}^{47}{Cr}$ ; prompt and delayed $γ - γ$ coincidences with $E_{{}^{3}{He}} = 22$ MeV. ${}^{40}{Ca} ({}^{12}C, α n) {}^{47}{Cr}$ ; prompt and delayed $γ - γ$ coincidences with $E_{{}^{12}C} = 38$ MeV. Deduced ${\frac{3}{2}}^{-}$ (g.s.), ${\frac{5}{2}}^{-} (99.3)$ , ${\frac{7}{2}}^{-} (174.7)$ , ${\frac{3}{2}}^{+} (471.5)$ , ${\frac{11}{2}}^{-} (1333.0)$ , ${\frac{15}{2}}^{-} (2655.3)$ , and $γ$ decay of these states.

Fusion-excitation-function analyses with a dynamic model

M. Blann and D. Akers

Phys. Rev. C 26, 465 (1982) - Published 1 August, 1982

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Sixteen heavy ion induced fusion excitation functions are analyzed using Swiatecki's new dynamic model. The systems selected span a target-projectile range between ${}^{12}C$ + ${}^{14}N$ to ${}^{86}{Kr}$ + ${}^{209}{Bi}$ . The effective threshold and extra energy parameters were held at the values deduced by Swiatecki from ${}^{208}{Pb}$ induced reactions, in order to display systematic scaling behavior with target and projectile mass and angular momentum. Agreement between experimental results and model predictions seem excellent for most systems investigated. A tendency to go from a rolling to sliding friction mode is noted as one goes to lighter systems. There is also some indication that the threshold parameter may decrease for lighter systems.

NUCLEAR REACTIONS Heavy ion fusion excitation functions, compared with predictions of new dynamic fusion model of Swiatecki.

Statistical fission parameters for nuclei at high excitation and angular momenta

M. Blann and T. T. Komoto

Phys. Rev. C 26, 472 (1982) - Published 1 August, 1982

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Experimental fusion/fission excitation functions are analyzed by the statistical model with modified rotating liquid drop model barriers and with single particle level densities modeled for deformation for ground state ( $a_{ν}$ ) and saddle point nuclei ( $a_{f}$ ). Values are estimated for the errors in rotating liquid drop model barriers for the different systems analyzed. These results are found to correlate well with the trends predicted by the finite range model of Krappe, Nix, and Sierk, although the discrepancies seem to be approximately 1 MeV greater than the finite range model predictions over the limited range tested. The a priori values calculated for $a_{f}$ and $a_{ν}$ are within ±2% of optimum free parameter values. Analyses for barrier decrements explore the importance of collective enhancement on level densities and of nuclear deformation in calculating transmission coefficients. A calculation is performed for the ${}^{97}{Rh}$ nucleus for which a first order angular momentum scaling is used for the $J = 0$ finite range corrections. An excellent fit is found for the fission excitation function in this approach. Results are compared in which rotating liquid drop model barriers are decremented by a constant energy, or alternatively multiplied by a constant factor. Either parametrization is shown to be capable of satisfactorily reproducing the data although their $J = 0$ extrapolated values differ markedly from one another. This underscores the dangers inherent in arbitrary barrier extrapolations.

NUCLEAR REACTIONS Deduced corrections to rotating liquid drop model barriers for selected data sets via statistical model fitting. Considered uncertainties due to collective enhancement of level densities, deformation effects on transmission coefficients. Compared deduced corrections to predictions of the finite range model.

Description of large angle ${}^{6}{Li}$ + ${}^{40}{Ca}$ scattering from 26 to 34 MeV using double-folded and $α + d$ cluster potentials

J. Cook, K. W. Kemper, and M. F. Vineyard

Phys. Rev. C 26, 486 (1982) - Published 1 August, 1982

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New elastic scattering data are reported for ${}^{6}{Li}$ + ${}^{40}{Ca}$ at 26 and 30 MeV, and inelastic data at 30 MeV. The measurements at 30 MeV were taken to provide a complete angular distribution at this energy and showed that previously published large angle data at 30 MeV are incorrectly normalized and must be multiplied by 0.65. The new angular distribution at 26 MeV displays enhanced large angle cross sections as has also been previously observed at 30 and 34 MeV. Double-folded or cluster potentials are able to describe the elastic scattering of ${}^{6}{Li}$ + ${}^{40}{Ca}$ over the energy range 26-34 MeV, including the large angle oscillations. No special property is required to explain the large angle behavior other than weak absorption. The double-folding model has also been used to determine deformation lengths for the first $2^{+}$ , $3^{-}$ , and $5^{-}$ states in ${}^{40}{Ca}$ . The values for the $2^{+}$ and $3^{-}$ states agree well with those found from electron, ${}^{9}{Be}$ and ${}^{11}B$ inelastic scattering, while the value for the $5^{-}$ state is a factor of 2 smaller.

NUCLEAR REACTIONS ${}^{40}{Ca}$ ( ${}^{6}{Li}$ , ${}^{6}{Li}$ ) ${}^{40}{Ca}$ , $E = 26$ MeV, $θ_{c . m .} = 9 ° - 161 °$ ; ${}^{40}{Ca}$ ( ${}^{6}{Li}$ , ${}^{6}{Li}$ ) ${}^{40}{Ca}$ * elastic and $3^{-}$ , $2^{+}$ , $5^{-}$ $E = 30$ MeV, $θ_{c . m .} = 9 ° - 78 °$ ; measured $σ (θ)$ . Double-folding model, cluster folding model, deduced optical model parameters; DWBA, deduced deformation lengths at 30 MeV.

Quadrupole moment of the $8^{-}$ isomer in ${}^{112}{Sb}$

H. -E. Mahnke, E. Dafni, M. H. Rafailovich, G. D. Sprouse, and E. Vapirev

Phys. Rev. C 26, 493 (1982) - Published 1 August, 1982

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The quadrupole interaction of the $8^{-}$ isomeric state ( $T_{\frac{1}{2}} = 536$ ns) in ${}^{112}{Sb}$ has been measured using the time differential perturbed angular distribution method. The linear momentum transfer from the ${}^{103}{Rh} ({}^{12}C, 3 n)$ reaction recoiled the isomeric nuclei into single crystals of Sb and Sn and a polycrystalline In foil. From the quadrupole coupling constant for the $8^{-}$ state of ${}^{112}{Sb}$ in Sb, the quadrupole moment was obtained relative to the moment of the stable ground state of ${}^{121}{Sb}$ : $| \frac{Q ({}^{112}{Sb}, 8^{-})}{Q ({}^{121}{Sb}, {\frac{5}{2}}^{+})} | = 1.958 (10)$ . The value is in accordance with the description of the isomer as an odd proton coupled to a neutron-excited Sn core. In addition, the measured coupling constants in Sn and In allow the determination of the quadrupole moments of isomers in ${}^{120, 122}{Sb}$ and ${}^{115}{Sb}$ .

NUCLEAR REACTIONS ${}^{103}{Rh} ({}^{12}C, 3 n) {}^{112}{Sb}$ , $E = 50$ MeV, pulsed beam, recoil implantation into Sb single crystal, Sn single crystal, In; measured $I_{γ} (θ, t)$ quadrupole modulation; deduced $Q$ .

Strong population of excited $0^{+}$ states in even Zr isotopes observed with the ( ${}^{14}C$ , ${}^{16}O$ ) reaction

Wolfgang Mayer, D. Pereira, K. E. Rehm, H. J. Scheerer, H. J. Körner, G. Korschinek, Waltraud Mayer, P. Sperr, Steven C. Pieper, and R. D. Lawson

Phys. Rev. C 26, 500 (1982) - Published 1 August, 1982

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The two-proton pickup reaction ( ${}^{14}C$ , ${}^{16}O$ ) on the even Mo isotopes was investigated at $E_{lab} = 71$ MeV. It was found that the ratio of the ground and first excite $O^{+}$ state cross sections changes dramatically as neutrons are added to the $N = 50$ shell. While the reaction ${}^{92}{Mo}$ ( ${}^{14}C$ , ${}^{16}O$ ) ${}^{90}{Zr}$ populates the ground state three times more strongly than the first excited $O^{+}$ state, for the heaviest isotope ${}^{98}{Zr}$ , the excited $O^{+}$ state has twice the population of the ground state. Attempts to explain the cross section ratios by means of distorted-wave Born approximation calculations, based on a complete Brody-Moshinsky decomposition of the two-proton cluster and spherical shell model wave functions, were not successful.

NUCLEAR REACTIONS ${}^{92, 100}{Mo}$ ( ${}^{14}C$ , ${}^{14}C$ ) ${}^{92, 100}{Mo}$ , $E_{lab} = 71$ MeV; measured $σ (θ)$ ; elastic and inelastic scattering; ${}^{92, 94, 96, 98, 100}{Mo}$ ( ${}^{14}C$ , ${}^{16}O$ ) ${}^{90, 92, 94, 96, 98}{Zr}$ reactions; optical model, DWBA calculations.

Target fragment angular distributions from the interaction of 3.0 GeV and 12.0 GeV ${}^{12}C$ with ${}^{197}{Au}$ and ${}^{238}U$

Y. Morita, W. Loveland, P. L. McGaughey, and G. T. Seaborg

Phys. Rev. C 26, 511 (1982) - Published 1 August, 1982

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Target fragment angular distributions have been measured using radioanalytical techniques for the interaction of 3.0 and 12.0 GeV ${}^{12}C$ with ${}^{197}{Au}$ and ${}^{238}U$ . For the reaction of 3.0 GeV ${}^{12}C$ ions with ${}^{197}{Au}$ and ${}^{238}U$ , angular distributions were obtained for eight different target fragments ( $89 \leq A \leq 155$ ), and seven different target fragments ( $43 \leq A \leq 149$ ), respectively. In the interaction of 12.0 GeV ${}^{12}C$ with ${}^{197}{Au}$ and ${}^{238}U$ , the angular distributions of six different target fragments ( $43 \leq A \leq 155$ ) from each target were measured. All the fragments observed from ${}^{197}{Au}$ target fragmentation show forward peaked angular distributions; from ${}^{238}U$ target fragmentation, typical neutron-rich fission fragment nuclides show isotropic distributions in the laboratory system, while the rest of the fragments show forward peaked distributions similar to those observed in ${}^{197}{Au}$ target fragmentation. The observed angular distributions are consistent with the values of previously measured $\frac{F}{B}$ ratios and are compared with predictions of the intranuclear cascade model. The measured angular distributions are used to test the validity of two step vector model of high energy reactions.

NUCLEAR REACTIONS Relativistic heavy ion reaction, target fragmentation, target fragment angular distributions for 3.0 and 12.0 GeV ${}^{12}C$ + ${}^{197}{Au}$ , ${}^{238}U$ ; two step vector model, intranuclear cascade model.

Mass dependence of the proton inclusive cross section for high energy nucleus-nucleus collisions

Bernd Schürmann and Norma Mankoč-Borštnik

Phys. Rev. C 26, 519 (1982) - Published 1 August, 1982

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We show that while the mass number dependences of the proton inclusive cross section measured in collisions of near-equal mass nuclei at 800 MeV/nucleon can, over a wide range of energies, be reproduced reasonably well by simplified multiple scattering models based on independent nucleon nucleon collisions, definite discrepancies show up at very high transverse momentum. Possible reasons for these deviations are discussed.

NUCLEAR REACTIONS Inclusive cross section, high transverse momenta, mass number dependence.

Spectroscopic strengths for ${}^{6}{Li}$ -induced alpha-particle transfers on ${}^{18}O$ at 72 MeV

T. Tanabe, K. Ogino, Y. Kadota, K. Haga, T. Kitahara, and T. Shiba

Phys. Rev. C 26, 524 (1982) - Published 1 August, 1982

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The ${}^{18}O ({}^{6}{Li}, d) {}^{22}{Ne}$ reaction has been studied at 72-MeV bombarding energy. The angular distributions for transitions to low-lying states in ${}^{22}{Ne}$ are fitted by exact finite-range distorted-wave Born approximation calculations and yield relative spectroscopic factors in good agreement with theoretical predictions.

NUCLEAR REACTIONS ${}^{18}O ({}^{6}{Li}, d) {}^{22}{Ne}$ , $E = 72$ MeV measured $σ (θ)$ . DWBA analysis, spectroscopic factors.

Lifetime of interference effects in collisional time-dependent Hartree-Fock dynamics

C. O. Dorso and E. S. Hernández

Phys. Rev. C 26, 528 (1982) - Published 1 August, 1982

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A kinetic equation in operator form for the one body density matrix is derived by means of a convenient truncation of the quantal Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy. Using projection techniques in a procedure similar to the derivation of the master equation, the evolution of the diagonal and the nondiagonal terms of the density matrix can be disentangled. A quantal, non-Hermitian master equation for the diagonal part is extracted and it is seen that corrections to the collision frequency or to the relaxation time arise as a consequence of the creation and destruction of incoherent events.

NUCLEAR REACTIONS Reduced one body density matrix, BBGKY hierarchy, quantal kinetic equation, coupling between probabilistic and interference matrix element, collision frequency and relaxation time, dynamical quantal corrections.

Entrance channel effect for complete fusion of O + C isotopes

B. Heusch, C. Beck, J. P. Coffin, P. Engelstein, R. M. Freeman, G. Guillaume, F. Haas, and P. Wagner

Phys. Rev. C 26, 542 (1982) - Published 1 August, 1982

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The cross section for total fusion of the reaction ${}^{18}O$ + ${}^{12}C$ was studied over a large range of energies from near the Coulomb barrier $B_{C}$ to $\sim 6 B_{C}$ . Good agreement was found between the critical angular momenta deduced from the experimental results and the predictions of different models. The reaction ${}^{17}O$ + ${}^{13}C$ , leading to the same compound nucleus ${}^{30}{Si}$ , was studied in the second fusion region (above $\sim 2 B_{C}$ ). By comparing the relative cross sections for fusion-evaporation to each isotope it is shown that for different entrance channels, even at the highest energies studied, the reactions appear to pass by the formation of a compound nucleus. The critical angular momenta were found to be systematically different from ${}^{18}O$ + ${}^{12}C$ . This difference, which may be due partially to the entrance channel spin, is interpreted as arising from the effect of direct reactions diverting flux from the compound nuclear processes.

NUCLEAR REACTIONS ${}^{16}O$ , ${}^{17}O$ , and ${}^{18}O$ beams on ${}^{14}C$ , ${}^{13}C$ , and ${}^{12}C$ targets, respectively; natural and enriched targets; $E_{lab} = 32 to 140$ MeV; time of flight with $Z$ identification technique; fusion evaporation and direct cross section measurements from $Z = 5 to 14$ and $A = 10 to 29$ ; statistical model calculations; entrance channel effects discussed; macroscopic model results for total fusion cross sections.

Nucleon excitation in low energy $π N \to γ γ N$

Doug Beder

Phys. Rev. C 26, 555 (1982) - Published 1 August, 1982

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The process $π + N \to 2 γ + N$ is investigated at low (50 MeV pion kinetic energy) energies, motivated by (nuclear) experiments in progress. Particular attention is given to contributions of the $Δ$ excitation of the nucleon, which is also included in a computer calculation of the lowest order perturbation theory amplitudes. The $Δ$ amplitudes enhance the calculated rate by 10-25% typically, a result which is slightly smaller than the $Δ$ contribution to the corresponding single photon process at the same energy.

NUCLEAR REACTIONS $π N \to γ γ N$ , $E_{π} = 50$ MeV; calculated contributions of $Δ$ resonance amplitudes via Lagrangian field theory.

Role of $π^{0} η^{'}$ mixing in nuclear charge asymmetry

Sidney A. Coon and Michael D. Scadron

Phys. Rev. C 26, 562 (1982) - Published 1 August, 1982

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We show that if all aspects of semistrong and electromagnetic particle mixing are properly taken into account, the result is that the $π^{0} η$ and $π^{0} η^{'}$ contributions to charge asymmetry of the nucleon force do not substantially modify the charge asymmetric $NN$ scattering lengths due to $π^{0} η$ mixing alone, and the $π^{0} η^{'}$ effect is $\sim \frac{1}{3}$ the (already small) $π^{0} η$ contribution to the ${}^{3}{He}$ - ${}^{3}H$ mass difference.

NUCLEAR REACTIONS Charge asymmetric nuclear forces, electromagnetic mixing of pseudoscalar mesons, effects in two-nucleon and three-nucleon systems.

Three-body approach to pionic ${}^{16}O$

J. de Kam and C. K. Wafelbakker

Phys. Rev. C 26, 570 (1982) - Published 1 August, 1982

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Relativistic three-body calculations are presented for the real part of the $π$ - ${}^{16}O$ scattering length. The effects of the nucleon binding and the exclusion principle are studied in the framework of a covariant three-body model (pion, nucleon, and core) of the optical potential. The present theory is a natural generalization of the optical potential model of Celenza, Liu, and Shakin who consider only the single-triangle diagram, ignoring the nucleon rescattering. We find that the nucleon binding and the exclusion principle each have a large effect on the scattering length. However, the combined effect of both medium corrections is much smaller. Depending on the model for the $π N$ $t$ matrix, the single-triangle diagram alone accounts for 15% and 33% of the scattering length. With medium correction included, these numbers are 25% and 40%, respectively. Finally, we determined the $s$ wave strength parameter $B_{0}$ in a phenomenological $ρ^{2}$ term.

NUCLEAR REACTIONS Three-body model, nucleon binding effects, exclusion-principle corrections, pion-nucleus optical potential, pion- ${}^{16}O$ scattering length.

Relativistic nucleon exchange in backward $p - d$ scattering

B. D. Keister and J. A. Tjon

Phys. Rev. C 26, 578 (1982) - Published 1 August, 1982

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The nucleon-exchange contribution to backward-angle $p - d$ scattering is evaluated as a Feynman diagram, in which the $d - n - p$ vertex function is obtained from recent numerical solutions to a bound-state Bethe-Salpeter equation. Comparisons are made to experimental cross section and polarization data, as well as to previous relativistic and nonrelativistic calculations.

NUCLEAR REACTIONS Backward-angle $p - d$ scattering and polarization. Relativistic and negative-energy effects. Bethe-Salpeter equation.

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Recent Issues

Mechanisms for composite particle production in nuclear reactions using ( $α, α^{'} x$ ) reactions up to 40 MeV/nucleon

High-spin states in ${}^{60}{Cu}$

${}^{180}{Ta}^{g, m}$ production cross sections from the ${}^{180}{Hf} (p, n)$ reaction

${}^{74}{Ge} (p, α) {}^{71}{Ga}$ reaction at 36.25 MeV.

Photoproton decay of the ${}^{45}{Sc}$ giant dipole resonance

$γ$ decay of states in ${}^{47}{Cr}$

Fusion-excitation-function analyses with a dynamic model

Statistical fission parameters for nuclei at high excitation and angular momenta

Description of large angle ${}^{6}{Li}$ + ${}^{40}{Ca}$ scattering from 26 to 34 MeV using double-folded and $α + d$ cluster potentials

Quadrupole moment of the $8^{-}$ isomer in ${}^{112}{Sb}$

Strong population of excited $0^{+}$ states in even Zr isotopes observed with the ( ${}^{14}C$ , ${}^{16}O$ ) reaction

Target fragment angular distributions from the interaction of 3.0 GeV and 12.0 GeV ${}^{12}C$ with ${}^{197}{Au}$ and ${}^{238}U$

Mass dependence of the proton inclusive cross section for high energy nucleus-nucleus collisions

Spectroscopic strengths for ${}^{6}{Li}$ -induced alpha-particle transfers on ${}^{18}O$ at 72 MeV

Lifetime of interference effects in collisional time-dependent Hartree-Fock dynamics

Entrance channel effect for complete fusion of O + C isotopes

Nucleon excitation in low energy $π N \to γ γ N$

Role of $π^{0} η^{'}$ mixing in nuclear charge asymmetry

Three-body approach to pionic ${}^{16}O$

Relativistic nucleon exchange in backward $p - d$ scattering

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