Recent Articles

Fusion cross section for ${}^{28}{Si}$ + ${}^{12}C$

Y. Nagashima, S. M. Lee, M. Sato, J. Schimizu, T. Nakagawa, Y. Fukuchi, K. Furuno, M. Yamanouchi, and T. Mikumo

Phys. Rev. C 26, 2661 (1982) - Published 1 December, 1982

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Fusion cross sections have been measured for the system ${}^{28}{Si}$ + ${}^{12}C$ from 50 to 105 MeV. No markedly smaller fusion cross sections were observed in comparison with the previously reported results for the other isotope systems ${}^{12}C$ + ${}^{29, 30}{Si}$ . Furthermore, the average energy dependence of the fusion cross sections for the three systems are well reproduced by the fusion barrier model with the same parameters. The maximum fusion cross sections for these systems are also well interpreted in terms of the statistical yrast line model.

NUCLEAR REACTIONS ${}^{28}{Si}$ + ${}^{12}C$ , $E_{lab} = 50 - 105$ MeV, measured fusion cross section, compared with fusion barrier, and statistical yrast line models.

Fusion cross sections for the ${}^{12}C$ + ${}^{15}N$ system

R. Novotny, D. Shapira, Y-d. Chan, D. E. DiGregorio, J. L. C. Ford, Jr., J. Gomez del Campo, M. E. Ortiz, and F. Pougheon

Phys. Rev. C 26, 2664 (1982) - Published 1 December, 1982

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Fusion cross sections were measured for the ${}^{12}C$ + ${}^{15}N$ system at two ${}^{12}C$ bombarding energies, 98 and 117 MeV. The extracted fusion cross sections are 946 ± 74 mb for $E ({}^{12}C) = 98$ MeV and 889 ± 89 mb for $E ({}^{12}C) = 117$ MeV. The critical angular momenta for fusion deduced from the cross section measurements equal, within $1 ℏ$ , the values deduced from ${}^{14}N$ + ${}^{13}C$ and ${}^{10}B$ + ${}^{17}O$ at the same excitation energies, thus indicating a compound nucleus limitation for fusion.

NUCLEAR REACTIONS ${}^{12}C$ + ${}^{15}N$ , $E ({}^{12}C) = 98 and 117$ MeV; gas cell target; measured $\frac{d^{2} σ}{d Ω dE}$ for reaction products with $Z = 7 to 12$ . Extracted $σ_{fus}$ .

$Q$ values for proton- and deuteron-induced reactions on selenium targets

J. D. Zumbro, A. A. Rollefson, R. W. Tarara, and C. P. Browne

Phys. Rev. C 26, 2668 (1982) - Published 1 December, 1982

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$Q$ values were measured for nine reactions on targets of ${}^{78, 80, 82}{Se}$ with uncertainties of 2.3 to 4.3 keV. Uncertainties for six of these measurements are smaller than those calculated from the 1976 mass excesses. The present $Q$ -value measurements, when combined with previous measurements, result in decreases of the masses of ${}^{82}{Se}$ , ${}^{83}{Se}$ , and ${}^{83}{Br}$ by 11, 67, and 16 keV, respectively.

NUCLEAR REACTIONS ${}^{80}{Se} (d, p) {}^{81}{Se}$ , ${}^{78, 80, 82}{Se} (p, d) {}^{77, 79, 81}{Se}$ , ${}^{78, 80, 82}{Se} (p, t) {}^{76, 78, 80}{Se}$ , ${}^{78, 80}{Se} (p, α) {}^{75, 77}{As}$ measured $Q$ values.

Nonlocality of the isobar propagation and the effective $Δ$ -nucleus spin-orbit interaction

M. Dillig, V. E. Herscovitz, and M. R. Teodoro

Phys. Rev. C 26, 2670 (1982) - Published 1 December, 1982

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The imaginary central and spin-orbit components of the $Δ$ -nucleus optical potential are investigated in a $π$ -exchange model. It is found that the effective spin-orbit interaction of the isobar reflects large nonlocalities from true pion absorption and from the quasielastic $Δ$ -decay. The parameters for the absorption and the spin-orbit strength are in qualitative agreement with recent phenomenological results.

NUCLEAR SCATTERING $Δ$ isobar propagation; relation of nonlocality and spin-orbit interaction.

Shape of the $α$ potentials in the distorted-wave Born approximation description of $α$ transfer

B. Gyarmati, K. F. Pál, and T. Vertse

Phys. Rev. C 26, 2674 (1982) - Published 1 December, 1982

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From many cases considered it is concluded that the exact shape of the equivalent deep attractive $α - A$ and $α - d$ potentials does not affect appreciably the distorted-wave Born approximation cross section of the $A ({}^{6}{Li}, d) B$ reaction.

NUCLEAR REACTION EFR DWBA cross section, various $α$ form factors.

Nuclear parameters for $π^{\pm}$ - ${}^{12}C$ scattering from Coulomb-nuclear interference

K. M. Das and B. B. Deo

Phys. Rev. C 26, 2678 (1982) - Published 1 December, 1982

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Forward nuclear amplitude for scattering of charged pions from ${}^{12}C$ nuclei has been calculated by extrapolation of the available data to the forward angle in the ( $\frac{3}{2}, \frac{3}{2}$ ) resonance region. The analysis is independent of any nuclear model. The values of $σ_{el}$ , $σ_{inel}$ , and ${[(\frac{d σ_{N}}{d Ω}) (0 °)]}_{el}$ are reported. Substantial difference, indicative of Coulomb distortion, is found for oppositely charged pions.

NUCLEAR REACTIONS ${}^{12}C (π^{\pm}, π^{\pm})$ , $T^{lab} = 115 - 280$ MeV; calculated forward nuclear amplitude, $σ_{el}$ , $σ_{inel}$ , ${[(\frac{d σ_{N}}{d Ω}) (0 °)]}_{el}$ , pole subtraction method.

Isosinglet $K^{+} N$ $S$ -wave scattering length

J. Sañudo

Phys. Rev. C 26, 2682 (1982) - Published 1 December, 1982

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Faddeev equations are used to analyze the available data of low-energy elastic $K^{+} d$ scattering in order to determine the isosinglet $K^{+} N$ $S$ -wave scattering length. For 107 MeV kaon lab kinetic energy the extracted $I = 0$ $S$ -wave scattering length is $a_{0} = - 0.015$ fm. The need of more precise experiments at lower energies is made clear.

NUCLEAR REACTIONS Faddeev equations; low-energy elastic $K^{+} d$ scattering; calculated $a_{0}$ .

Possible existence of a $π^{-} nn$ bound state

Humberto Garcilazo

Phys. Rev. C 26, 2685 (1982) - Published 1 December, 1982

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We have applied the relativistic Faddeev formalism to look for a bound state of a negative pion and two neutrons, using as input the pion-nucleon $P_{33}$ channel and the nucleon-nucleon ${}^{1}S_{0}$ channel. We found that if the pion-nucleon interaction is sufficiently short ranged, the system can be bound. We represented the pion-nucleon interaction with two different models of rank-one separable potentials, while for the nucleon-nucleon interaction we used the Yamaguchi potential and three different models of rank-two separable potentials.

NUCLEAR REACTIONS $π^{-} nn$ bound state; calculated, Fredholm determinant at $\sqrt{S} = 2018$ MeV.

Properties of the intrinsic matrix elements of the interacting-boson-approximation $E 2$ operator in the rotational limit

R. Bijker and A. E. L. Dieperink

Phys. Rev. C 26, 2688 (1982) - Published 1 December, 1982

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It is shown that the dominance of $β \to γ$ and $γ \to g$ over $β \to g$ $E 2$ transitions in the SU(3) limit of the interacting-boson-approximation model reported by Warner and Casten can be explained simply in terms of properties of the intrinsic $E 2$ matrix elements.

NUCLEAR STRUCTURE Properties of $E 2$ matrix elements in SU(3) limit of the interacting-boson-approximation model.

Reply to "Properties of the intrinsic matrix elements of the interacting-boson-approximation $E 2$ operator in the rotational limit"

D. D. Warner and R. F. Casten

Phys. Rev. C 26, 2690 (1982) - Published 1 December, 1982

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In this reply, we emphasize the importance of the results of Bijker and Dieperink, and point out several additional implications and applications of their approach, particularly with regard to the role of finite boson number in the interacting boson approximation.

NUCLEAR STRUCTURE Role of finite boson number in the interacting boson approximation.

Phase transitions in exactly soluble models

G. Bozzolo, J. Núñez, and A. Plastino

Phys. Rev. C 26, 2692 (1982) - Published 1 December, 1982

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A linearized version of the Hartree-Fock method is reinvestigated in order to develop a new technique for the study of phase transitions. This is studied with reference to an exactly soluble model, yielding excellent results.

NUCLEAR STRUCTURE Phase transitions. Approximate many body methods applied to a soluble model.

RAPID COMMUNICATION

Momentum transfer to the target in peripheral collisions of relativistic heavy ions

S. B. Kaufman, M. S. Freedman, D. J. Henderson, E. P. Steinberg, B. D. Wilkins, A. Baden, H. H. Gutbrod, M. R. Maier, J. Péter, H. G. Ritter, H. Stelzer, A. I. Warwick, H. H. Wieman, and F. Weik

Phys. Rev. C 26, 2694(R) (1982) - Published 1 December, 1982

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The angular correlations between coincident fission fragments emitted in the reactions of ${}^{197}{Au}$ with 5-GeV protons, 1.25-GeV/nucleon ${}^{4}{He}$ , and 0.25-2.10-GeV/nucleon ${}^{20}{Ne}$ were measured. The longitudinal momentum transfer to the target calculated from these correlations increased with increasing mass loss from the target and was inversely proportional to the projectile velocity, independent of projectile mass. These observations are shown to be consistent with simple two-body models of peripheral reactions.

NUCLEAR REACTIONS, FISSION $Au (p, f)$ , ( ${}^{4}{He}$ , $f$ ), ( ${}^{20}{Ne}$ , $f$ ), $E_{p, {}^{4}{He}} = 5$ , GeV, $E_{{}^{20}{Ne}} = 5 - 42$ GeV, measured angular correlations of coincident fragments; deduced momentum transfer to target.

RAPID COMMUNICATION

Quantitative test of the Lane-Lynn theory of direct radiative capture of thermal neutrons by ${}^{12}C$ and ${}^{13}C$

S. F. Mughabghab, M. A. Lone, and B. C. Robertson

Phys. Rev. C 26, 2698(R) (1982) - Published 1 December, 1982

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The Lane-Lynn theory of direct capture is subjected to a quantitative test in the radiative capture of thermal neutrons by ${}^{12}C$ and ${}^{13}C$ . Strong destructive interference effects are observed for the ground state transitions in ${}^{13}C$ and ${}^{14}C$ as predicted by the theory. An outcome of these investigations is the demonstration of the physical significance of the interaction radius. The theory was applied to deduce a ( $d, p$ ) spectroscopic factor of 0.060 ± 0.004 for the 6589 keV state of ${}^{14}C$ . In addition, the ratio of the radiative capture cross section of ${}^{13}C$ relative to ${}^{12}C$ was measured as 0.388 ± 0.010.

NUCLEAR REACTIONS ${}^{12, 13}C (n, γ)$ $E = thermal$ ; measured $σ_{γ}$ , $I_{γ}$ . ${}^{12, 13}C$ levels; verified Lane-Lynn theory of direct capture; deduced $S$ .

RAPID COMMUNICATION

Pion-induced nucleon knockout reactions on ${}^{16}O$ and ${}^{18}O$

E. Piasetzky, A. Altman, J. Lichtenstadt, A. I. Yavin, D. Ashery, W. Bertl, L. Felawka, H. K. Walter, F. W. Schlepütz, R. J. Powers, R. G. Winter, and J. v. d. Pluym

Phys. Rev. C 26, 2702(R) (1982) - Published 1 December, 1982

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The ( $π^{+}, π^{+} p$ ), ( $π^{-}, π^{-} p$ ), and ( $π^{-}, π^{-} n$ ) reactions on ${}^{16}O$ and ${}^{18}O$ were studied at 165 MeV by coincidence measurements of the outgoing particles. The cross sections for the ( $π^{-}, π^{-} n$ ) reaction is larger on ${}^{18}O$ than on ${}^{16}O$ , whereas those for the ( $π^{+}, π^{+} p$ ) and the ( $π^{-}, π^{-} p$ ) reactions are smaller, most likely because of the coupling between the absorption and the scattering channels.

NUCLEAR REACTIONS ( $π^{\pm}, π^{\pm} p$ ) ( $π^{-}, π^{-} n$ ) coin. Measurements on ${}^{16}O$ ${}^{18}O$ $E = 165$ MeV; deduced coupling between the absorption and the scattering channels.

RAPID COMMUNICATION

Yrast bands in light nuclei and the effective interactions in $J = 0, 2$ states

S. K. Sharma, V. Potbhare, and V. K. B. Kota

Phys. Rev. C 26, 2706(R) (1982) - Published 1 December, 1982

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The dominant role played by the effective interactions in angular momentum states with $J = 0, 2$ vis-á-vis the structure of the yrast states in the $2 s - 1 d$ and $2 p - 1 f - 1 g$ shell nuclei is pointed out.

NUCLEAR STRUCTURE Effective interactions in $J = 0, 2$ states. Structure of the yrast bands. Exact shell model calculations for ${}^{20 - 22}O$ , ${}^{20}{Ne}$ , and ${}^{60}{Ni}$ .

${}^{24}{Mg} (\vec{p}, d)$ analyzing-power measurements at 95 MeV

D. W. Miller, W. W. Jacobs, D. W. Devins, and W. P. Jones

Phys. Rev. C 26, 1793 (1982) - Published 1 November, 1982

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Analyzing-power angular distributions have been measured for prominent states excited by the ${}^{24}{Mg} (\vec{p}, d)$ reaction at 94.8-MeV bombarding energy. The distributions for the known low-lying hole states ( $E_{x} < 6$ MeV) exhibit a clear $j$ dependence with characteristic features which are most pronounced near 6° for $l = 1$ transitions, and near 35° for $l = 2$ transitions. The analyzing powers observed for $l = 0$ pickup are strongly oscillatory, reaching a value ≅0.9 near 20°. These measured spin signatures allow the identification of "deephole" $p$ states at 8.91-, 9.67-, and 10.57-MeV excitation in ${}^{23}{Mg}$ as ${p_{\frac{3}{2}}}^{- 1}$ and of a state at 9.02 MeV as ${p_{\frac{1}{2}}}^{- 1}$ . Difficulties in reproducing the behavior of the measured cross sections and analyzing powers using standard distorted-wave Born approximation calculations are apparent, particularly for $l = 0$ transitions.

NUCLEAR REACTIONS ${}^{24}{Mg} (\vec{p}, d)$ , $E = 94.8$ MeV; measured $A (θ)$ . ${}^{23}{Mg}$ levels deduced $J$ ; $E_{x} = 0 - 10.6$ MeV. Enriched targets, DWBA analysis, resolution 70 keV FWHM; $θ = 6 - 36 °$ , $Δ θ = 2 or 3 °$ .

Analysis of the ${}^{12}C (\vec{p}, p^{'}) {}^{12}C$ reaction at 200 MeV in the distorted-wave impulse approximation

J. R. Comfort, G. L. Moake, C. C. Foster, P. Schwandt, and W. G. Love

Phys. Rev. C 26, 1800 (1982) - Published 1 November, 1982

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Differential cross sections and analyzing powers are presented for discrete states of ${}^{12}C$ up to 21-MeV excitation energy as observed by the ${}^{12}C (\vec{p}, p^{'}) {}^{12}C$ reaction at 200 MeV. The results of distorted-wave, impulse-approximation calculations with a 210-MeV free nucleon-nucleon $t$ matrix are compared with the data for most of the transitions. The comparisons are divided into classes that emphasize different aspects of the effective interaction. As a whole, the comparisons are comparable to those at lower energies. However, the description of the 15.11-MeV transition to a $1^{+}$ , $T = 1$ state is decidedly inferior. The effects of removing abnormal-parity amplitudes with $S = 1$ are considered for several transitions. In particular, their removal produces good agreement for the 15.11-MeV state.

NUCLEAR REACTIONS ${}^{12}C (\vec{p}, p^{'}) {}^{12}C$ , $E = 200$ MeV, measured $σ (E_{p}, θ)$ , $A_{y} (E_{p}, θ)$ ; $θ = 6 ° - 60 °$ , $E_{x} = 0 - 21$ MeV. DWIA analysis.

Phase shift behavior at degenerate continuum bound states

L. L. Foldy

Phys. Rev. C 26, 1818 (1982) - Published 1 November, 1982

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A special case of a nonlocal potential which has a degenerate continuum bound state is studied using the Bolsterli criterion for defining the phase shift, and is found to be consistent with Levinson's theorem and the Wigner inequality.

NUCLEAR REACTIONS Phase shift behavior for nonlocal potentials, degenerate continuum bound states, Levinson's theorem.

Mechanism of cluster emission in nucleon-induced preequilibrium reactions

A. Iwamoto and K. Harada

Phys. Rev. C 26, 1821 (1982) - Published 1 November, 1982

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A model is proposed for the preequilibrium emission of light composite particles in the framework of the exciton model. The model contains two new points: One is the calculation of the formation factor $F_{l, m} (ε)$ which stands for the probability that the composite particle of an energy $ε$ is composed of $l$ particles above the Fermi level and $m$ particles below. Information of the intrinsic wave function of the composite particle is incorporated in the $F_{l, m} (ε)$ . Another new point is the inclusion of the pickup type contribution in the particle emission mechanism. We allow some nucleons which constitute the emitted composite particle to come from levels below the Fermi energy. This model is applied to six kinds of ( $p, α$ ) reactions of incident energies of several tens of MeV on ${}^{54}{Fe}$ , ${}^{118}{Sn}$ , and ${}^{120}{Sn}$ targets. Calculated results reproduce nicely the high energy part of the experimental energy spectra and indicate that its main component is the "three-particle pickup" reaction coming from $2 p - 1 h$ and $3 p - 2 h$ , but "two-particle pickup" also contributes substantially.

NUCLEAR REACTIONS Exciton model, composite particle emission mechanism; ${}^{54}{Fe} (p, α)$ , ${}^{118}{Sn} (p, α)$ , ${}^{120}{Sn} (p, α)$ , $E = 29 - 62$ MeV; calculated $σ (E, E_{α})$ .

Sigma set scattering equations in nuclear reaction theory

K. L. Kowalski and A. Picklesimer

Phys. Rev. C 26, 1835 (1982) - Published 1 November, 1982

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The practical applications of partially summed versions of the Rosenberg equations involving only special subsets (sigma sets) of the physical amplitudes are investigated with special attention to the Pauli principle. The requisite properties of the transformations from the pair labels to the set of partitions labeling the sigma set of asymptotic channels are established. New, well-defined, scattering integral equations for the antisymmetrized transition operators are found which possess much less coupling among the physically distinct channels than hitherto expected for equations with kernels of equal complexity. In several cases of physical interest in nuclear physics, a single connected-kernel equation is obtained for the relevant antisymmetrized elastic scattering amplitude.

NUCLEAR REACTIONS Rosenberg equations, Pauli principle in nuclear reaction theory.

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Fusion cross section for ${}^{28}{Si}$ + ${}^{12}C$

Fusion cross sections for the ${}^{12}C$ + ${}^{15}N$ system

$Q$ values for proton- and deuteron-induced reactions on selenium targets

Nonlocality of the isobar propagation and the effective $Δ$ -nucleus spin-orbit interaction

Shape of the $α$ potentials in the distorted-wave Born approximation description of $α$ transfer

Nuclear parameters for $π^{\pm}$ - ${}^{12}C$ scattering from Coulomb-nuclear interference

Isosinglet $K^{+} N$ $S$ -wave scattering length

Possible existence of a $π^{-} nn$ bound state

Properties of the intrinsic matrix elements of the interacting-boson-approximation $E 2$ operator in the rotational limit

Reply to "Properties of the intrinsic matrix elements of the interacting-boson-approximation $E 2$ operator in the rotational limit"

Phase transitions in exactly soluble models

Momentum transfer to the target in peripheral collisions of relativistic heavy ions

Quantitative test of the Lane-Lynn theory of direct radiative capture of thermal neutrons by ${}^{12}C$ and ${}^{13}C$

Pion-induced nucleon knockout reactions on ${}^{16}O$ and ${}^{18}O$

Yrast bands in light nuclei and the effective interactions in $J = 0, 2$ states

${}^{24}{Mg} (\vec{p}, d)$ analyzing-power measurements at 95 MeV

Analysis of the ${}^{12}C (\vec{p}, p^{'}) {}^{12}C$ reaction at 200 MeV in the distorted-wave impulse approximation

Phase shift behavior at degenerate continuum bound states

Mechanism of cluster emission in nucleon-induced preequilibrium reactions

Sigma set scattering equations in nuclear reaction theory

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