Recent Articles

Negative-parity states in odd-mass lanthanum isotopes

S. Das Gupta and N. de Takacsy

Phys. Rev. C 10, 1220 (1974) - Published 1 September, 1974

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A semimicroscopic calculation is done to obtain the negative-parity states of odd-mass lanthanum isotopes. In agreement with a recently published calculation we find that a positive deformation is needed to explain the experimental data.

NUCLEAR STRUCTURE ${}^{129}{La}$ ; calculated levels as a function of deformation.

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Imaginary optical potential in ${}^{206}{Pb}$ and its comparison to ${}^{208}{Pb}$

Amos Lev and William P. Beres

Phys. Rev. C 10, 1223(R) (1974) - Published 1 September, 1974

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The imaginary optical potential and absorption cross section for neutrons on ${}^{206}{Pb}$ are calculated within the particle-vibration model using intermediate structure. The results are compared to those for ${}^{208}{Pb}$ and are quite similar. The relationship to the nuclear spreading width is discussed.

NUCLEAR REACTIONS ${}^{206, 208}{Pb} (n, n)$ , $E = 0 - 12$ MeV; calculated imaginary optical potential and absorption; discussed relation with $Γ^{↓}$ . Particle-vibration doorways.

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Galilean-invariance ambiguity in the nonrelativistic pion-nucleon absorption operator

M. Bolsterli, W. R. Gibbs, B. F. Gibson, and G. J. Stephenson, Jr.

Phys. Rev. C 10, 1225(R) (1974) - Published 1 September, 1974

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In the model of a nucleon interacting with a massive object via a potential in the Dirac equation, we have demonstrated that the behavior of the nonrelativistic pion absorption operator under Galilean transformations depends upon the properties of the potential under Lorentz transformations. In particular, the operator has a Galilean invariant form if the potential is the time-like component of a four-vector, but not if the potential is a scalar.

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Beta decay of ${}^{180}{Lu}$

T. E. Ward and J. M. D'Auria

Phys. Rev. C 10, 1227(R) (1974) - Published 1 September, 1974

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The allowed-unhindered $β$ decay of ${}^{180}{Lu}$ strongly suggests that the ${\frac{9}{2}}^{-} {[514]}_{p}$ , ${\frac{7}{2}}^{-} {[514]}_{n}$ Nilsson orbitals are involved in the transition. As a result of this proposed interpretation, the ground state Nilsson configuration of ${}^{180}{Lu}$ is most probably ${\frac{9}{2}}^{-} {[514]}_{p}$ , ${\frac{1}{2}}^{-} {[510]}_{n}$ with $K^{π} = 5^{+}$ , not ${\frac{7}{2}}^{+} [404]$ , ${\frac{1}{2}}^{-} {[510]}_{n}$ with $K^{π} = 3^{-}$ as previously suggested.

RADIOACTIVITY ${}^{180}{Lu}$ ; ${}^{180}{Hf}$ deduced levels, $J$ , $π$ . Calculated two-quasiparticle states ${}^{180}{Hf}$ .

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Core $M 1$ effect at $A = 14$

D. C. Peaslee and C. F. Williamson

Phys. Rev. C 10, 1229(R) (1974) - Published 1 September, 1974

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A recent measurement of ( $e, e$ ) scattering on ${}^{14}N$ supplies a new parameter, the $q^{2}$ dependence of $M 1$ excitation to the 2.313 MeV state. An exhaustive analysis precludes a satisfactory fit with the ${(1 p)}^{- 2}$ configuration. Comparison with ${}^{6}{Li}$ suggests appreciable core effects at $A = 14$ . Inclusion of the 15.1 MeV state in the ${}^{12}C$ core permits a generally acceptable fit, although with too great flexibility for uniqueness.

NUCLEAR STRUCTURE Lowest states of ${}^{14}N$ , ${}^{6}{Li}$ from ( $e, e^{'}$ ) analysis; core excitation model indicated for ${}^{14}N$ but not for ${}^{6}{Li}$ .

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Neutron strength of the 5.08-MeV ${\frac{3}{2}}^{+}$ state of ${}^{17}O$

H. T. Fortune and C. M. Vincent

Phys. Rev. C 10, 1233(R) (1974) - Published 1 September, 1974

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The data for the reaction ${}^{16}O (d, p) {}^{17}O$ to the unbound state at 5.08 MeV have been reanalyzed by using average sets of optical-model parameters and standard parameters for the transferred-particle well. Still, the neutron width extracted from the ( $d, p$ ) data is only $\frac{2}{3}$ of the measured width.

NUCLEAR STRUCTURE ${}^{16}O (d, p)$ (5.08 MeV), dependence of extracted spectroscopic factor on details of unbound DWBA calculation.

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Masses of technetium isotopes

J. R. Comfort, R. W. Finlay, C. M. McKenna, and P. T. Debevec

Phys. Rev. C 10, 1236(R) (1974) - Published 1 September, 1974

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Evidence for charge exchange coupling in ${}^{206}{Pb} (t, p) {}^{208}{Pb}$

E. M. Bernstein, A. Solomon, M. Soga, and D. D. Armstrong

Phys. Rev. C 10, 1239(R) (1974) - Published 1 September, 1974

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Anomalies are observed in the excitation function of the ${}^{206}{Pb} (t, p) {}^{208}{Pb}$ reaction measured at 169° lab from 9 to 16 MeV. In addition to isospin forbidden analog resonances, anomalous behavior is observed near the threshold for the analogous $t, n$ reaction. These results as well as previously reported data for other reactions are consistent with the interpretation of this latter anomaly as arising from charge exchange coupling.

NUCLEAR REACTIONS ${}^{206}{Pb} (t, p)$ , $E = 9 - 16$ MeV; measured $σ (E_{t})$ , $θ = 169 °$ .

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Angle transformation for the $π$ -nucleus optical potential

Gerald A. Miller

Phys. Rev. C 10, 1242(R) (1974) - Published 1 September, 1974

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A simplified form of the pion optical potential which includes the $p$ -wave threshold kinematics for the angle transformation is presented. Numerical results are given, and a comparison with the work of several others is made.

NUCLEAR REACTIONS $π^{- 12}$ -C scattering at 120 MeV, theoretical optical potential.

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Production of ${}^{8}{Be}$ in the reaction of 126-MeV ${}^{12}C$ with ${}^{197}{Au}$

R. L. Kozub, D. Logan, J. M. Miller, and A. M. Zebelman

Phys. Rev. C 10, 1246(R) (1974) - Published 1 September, 1974

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The cross section for the production of ${}^{8}{Be}$ (g.s.) in the ${}^{12}C$ + ${}^{197}{Au}$ reaction at 126-MeV bombarding energy has been measured as 37 ± 8 mb. Thus, the total observed Be cross section is about 40 mb less than the Tl cross section for the same entrance channel, which suggests a substantial cross section for excited states of ${}^{8}{Be}$ .

Erratum: Recoil effects in allowed nuclear beta decay

Barry R. Holstein, W. Shanahan, and S. B. Treiman

Phys. Rev. C 10, 1249 (1974) - Published 1 September, 1974

Erratum: Gamma-ray spectroscopy studies of ${}^{52}{Ti}$

J. G. Pronko, T. T. Bardin, J. A. Becker, T. R. Fisher, R. E. McDonald, and A. R. Poletti

Phys. Rev. C 10, 1249 (1974) - Published 1 September, 1974

Determination of the effective ${}^{12}C$ + ${}^{12}C$ potential from the sub-Coulomb single-particle resonances

J. Y. Park, W. Scheid, and W. Greiner

Phys. Rev. C 10, 967 (1974) - Published 1 September, 1974

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The sub-Coulomb resonances observed in the total reaction yield of the ${}^{12}C$ + ${}^{12}C$ system at 4.9, 5.6, and 6.2 MeV are explained as single-particle resonances. The "true" effective ${}^{12}C$ + ${}^{12}C$ potential is determined directly as the real potential which reproduces best the position and the spacing of the observed sub-Coulomb resonances. This potential is found from a parametrization of the two limiting adiabatic and sudden potentials.

Isospin-forbidden alpha decay of the 15.11-MeV state in ${}^{12}C$

D. P. Balamuth, R. W. Zurmühle, and S. L. Tabor

Phys. Rev. C 10, 975 (1974) - Published 1 September, 1974

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The branching ratio $\frac{Γ_{α}}{Γ_{total}}$ has been measured for the 15.11-MeV $1^{+}$ $T = 1$ state in ${}^{12}C$ . The result is $\frac{Γ_{α}}{Γ_{total}} = (4.1 \pm 0.9)$ %, in agreement with one previous measurement and in disagreement with another. The result was obtained by direct observation of the decay $α$ particles from the reaction ${}^{13}C ({}^{3}{He}, α) {}^{12}C^{*} \to 3 α$ . The data are consistent with a sequential decay via the first excited state of ${}^{8}{Be}$ . The $3 α$ breakup of the $1^{+}$ $T = 0$ state at $E_{x} = 12.71$ MeV was also studied. The data in both cases were fitted with a model in which the $α - α$ final state interaction was treated as a simple Breit-Wigner resonance; order-of-emission interference effects were included. If the (isospin-forbidden) $α$ width is interpreted as resulting from mixing between the two $1^{+}$ states via a charge-dependent interaction, a large isospin-violating matrix element is involved.

NUCLEAR REACTIONS ${}^{13}C ({}^{3}{He}, α) {}^{12}C^{*} (α_{1}) {}^{8}{Be}^{*} (α_{2}) α_{3}$ , $E = 15$ MeV, $α - α$ coincidence, deduced $\frac{Γ_{α}}{Γ_{total}}$ for 15.11-MeV level of ${}^{12}C$ .

Distortion effects in $α + α$ system

D. R. Thompson, Y. C. Tang, and F. S. Chwieroth

Phys. Rev. C 10, 987 (1974) - Published 1 September, 1974

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$α$ -particle specific distortion effects in the $α + α$ system are examined by the addition of square-integrable distortion functions into the usual resonating-group formulation. The results indicate that such effects are not too important and can be neglected in calculations on other light nuclear systems.

NUCLEAR REACTIONS ( ${}^{4}{He} (α, α)$ ), $E = 0 - 20$ MeV; calculated phase shifts. Resonating-group method with specific distortion effects.

States in ${}^{29}P$ via the ${}^{32}S (p, α) {}^{29}P$ reaction

N. A. Detorie, J. D. Goss, A. A. Rollefson, and C. P. Browne

Phys. Rev. C 10, 991 (1974) - Published 1 September, 1974

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$α$ particles from the ${}^{32}S (p, α)$ reaction were momentum analyzed with our 100-cm modified broad range magnetic spectrograph to determine accurate excitation energies in ${}^{29}P$ . Runs were taken at laboratory observation angles of 60, 90, and 120° using protons with nominal bombarding energies of 15 and 16 MeV. Five previously unreported levels in ${}^{29}P$ were identified at 4.6406 ± 0.0030, 5.0473 ± 0.0032, 5.5827 ± 0.0035, 5.7155 ± 0.0036, and 5.8259 ± 0.0048 MeV. Comparisons are made both with theoretical level calculations and the level structure of the conjugate nucleus ${}^{29}{Si}$ . A Breit-Wigner shape was used to fit the group at 4.3371 MeV; the width of this level was determined to be 48.7 ± 2.5 keV.

NUCLEAR REACTIONS ${}^{32}S (p, α)$ $E_{p} = 15 and 16$ MeV; $θ_{lab} = 60, 90, and 120 °$ . Measured excitation energies; deduced five previously unreported levels below 6 MeV.

Lifetimes of the ${(f_{\frac{7}{2}})}^{3} {\frac{15}{2}}^{-}$ states in ${}^{51}V$ and ${}^{43}{Ca}$ and ${(f_{\frac{7}{2}})}^{2} 4^{+}$ states in ${}^{50}{Ti}$ and ${}^{42}{Ca}$ via heavy-ion recoil-distance-method measurements

A. R. Poletti, B. A. Brown, D. B. Fossan, P. Gorodetzky, J. J. Kolata, J. W. Olness, and E. K. Warburton

Phys. Rev. C 10, 997 (1974) - Published 1 September, 1974

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The recoil-distance method has been used in conjunction with heavy-ion reactions to measure the following mean lifetimes: $τ = 8.0 \pm 0.6 and 34.1 \pm 1.5$ psec for the ${(f_{\frac{7}{2}})}^{3}$ ( ${\frac{15}{2}}^{-}$ ) states at 2700 keV in ${}^{51}V$ and at 2754 keV in ${}^{43}{Ca}$ , and $τ = 7.7 \pm 1.5 and 5.1 \pm 0.4$ psec for the ${(f_{\frac{7}{2}})}^{2} 4^{+}$ states at 2676 keV in ${}^{50}{Ti}$ and at 2752 keV in ${}^{42}{Ca}$ , respectively. The resulting $B (E 2)$ strengths are interpreted in terms of effective charges for different model spaces.

NUCLEAR REACTIONS ${}^{48}{Ca} ({}^{6}{Li}, 3 n)$ $E = 26$ MeV, ${}^{48}{Ca} ({}^{6}{Li}, p 3 n)$ $E = 26$ MeV, ${}^{48}{Ca} ({}^{7}{Li}, 4 n)$ $E = 28$ MeV, ${}^{27}{Al} ({}^{18}O, p n)$ $E = 30, 35$ MeV, ${}^{27}{Al} ({}^{18}O, p 2 n)$ $E = 30, 35$ MeV, ${}^{27}{Al} ({}^{19}F, 2 p n)$ $E = 36$ MeV; measured recoil distance. Deduced $T_{\frac{1}{2}}$ , $B (E 2)$ , effective charges. Natural and enriched targets, Ge(Li) detector.

Energy-dependent-core model for attenuation effects in quasifree scattering

R. D. Haracz and T. K. Lim

Phys. Rev. C 10, 431 (1974) - Published 1 August, 1974

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A new model for attenuation effects in quasifree scattering in the reactions ${}^{2}H (p, 2 p) n$ , ${}^{3}{He} (p, 2 p) d$ , ${}^{4}{He} (p, 2 p) {}^{3}H$ , ${}^{6}{Li} (α, 2 α) d$ , and ${}^{6}{Li} (p, p α) d$ is proposed. The attenuation of events from the primary quasifree reaction occurs through the rescattering of the emerging quasifree particles by the spectator nucleus $S$ . These particles and $S$ are represented by core regions of strong interaction, the sizes of which are directly related to their total cross sections. Good agreement with the experimental results of Pugh et al. is obtained.

NUCLEAR REACTIONS ${}^{2}H$ , ${}^{3, 4}{He} (p, 2 p)$ , $E = 20 - 60$ MeV; ${}^{6}{Li} (p, p α) d$ , $E = 57$ MeV; ${}^{6}{Li} (α, 2 α) d$ , $E = 55$ MeV; calculated $σ$ .

Relativistic wave functions for pion-nucleon and pion-nucleus scattering

L. S. Celenza, M. K. Liou, L. C. Liu, and C. M. Shakin

Phys. Rev. C 10, 435 (1974) - Published 1 August, 1974

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We use a modification of the method of Blankenbecler and Sugar to discuss various reductions of the Bethe-Salpeter equation to three-dimensional equations. Pion-nucleon and pion-nucleus scattering are treated, and the advantages of the use of different Green's functions are indicated. For the case of pion-nucleus scattering we propose a relativistic impulse approximation for use in construction of a relativistic optical model. The relations of the wave functions resulting from the solution of the three-dimensional equations to the Bethe-Salpeter wave function is indicated. Our method should be particularly useful in providing a frame-work in which phenomenological studies of the off-shell pion-nucleon $T$ matrices may be made, since the relationship of our (relativistic) three-dimensional equations to a manifestly covariant theory has been made explicit.

NUCLEAR REACTIONS Three-dimensional covariant equations for pion-nucleon and pion-nucleus systems; relativistic multiple scattering theory.

Energy dependence of two-nucleon transfer reactions on light nuclei

M. Pignanelli, S. Micheletti, I. Iori, P. Guazzoni, F. G. Resmini, and J. L. Escudié

Phys. Rev. C 10, 445 (1974) - Published 1 August, 1974

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The differential cross section has been measured at several incident proton energies between 20 and 45 MeV for the ${}^{14}N (p, {}^{3}{He}) {}^{12}C$ , ${}^{15}N (p, t) {}^{13}N$ , ${}^{15}N (p, {}^{3}{He}) {}^{13}C$ , and ${}^{18}O (p, t) {}^{16}O$ reactions. Data on the energy dependence of other transfer reactions on the same nuclei, i.e., ${}^{18}O (p, d) {}^{17}O$ , ${}^{14}N (p, α) {}^{11}C$ , and ${}^{18}O (p, α) {}^{15}N$ reactions have also been obtained. These data are compared with distorted wave Born approximation (DWBA) predictions. The comparison indicates that the energy dependence of the cross sections is poorly explained by DWBA calculations based on single-step pickup which give a maximum in the cross section in the energy region where angular momentum matching conditions are achieved. The absence of corresponding maxima in the experimental excitation functions may indicate that other reaction mechanisms contribute substantially to the cross section. Theoretical approaches as successive pickup of the nucleons and preequilibrium emission are also discussed.

NUCLEAR REACTIONS ${}^{14}N (p, {}^{3}{He})$ , ( $p, α$ ), $E = 20.5 - 44.6$ MeV; measured $σ (E_{{}^{3}{He}}, θ)$ ; resolution 200 KeV, $θ_{lab} = 12 - 166 °$ . Reaction mechanism analysis. ${}^{15}N (p, t)$ , $p, {}^{3}{He}$ , $E = 24.0 - 43.5$ MeV; measured $σ (E_{t}, θ)$ , $σ (E_{{}^{3}{He}}, θ)$ ; resolution 200 keV, $θ_{lab} = 12 - 126 °$ . Enriched target. Reaction mechanism analysis. ${}^{18}O (p, d)$ , ( $p, t$ ), ( $p, α$ ), $E = 20.0 - 43.6$ MeV; measured $σ (E_{d}, θ)$ , $σ (E_{t}, θ)$ , $σ (E_{α}, θ)$ ; resolution 200 keV, $θ_{lab} = 14 - 164 °$ . Enriched target. Reactin mechanism analysis.

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Negative-parity states in odd-mass lanthanum isotopes

Imaginary optical potential in ${}^{206}{Pb}$ and its comparison to ${}^{208}{Pb}$

Galilean-invariance ambiguity in the nonrelativistic pion-nucleon absorption operator

Beta decay of ${}^{180}{Lu}$

Core $M 1$ effect at $A = 14$

Neutron strength of the 5.08-MeV ${\frac{3}{2}}^{+}$ state of ${}^{17}O$

Masses of technetium isotopes

Evidence for charge exchange coupling in ${}^{206}{Pb} (t, p) {}^{208}{Pb}$

Angle transformation for the $π$ -nucleus optical potential

Production of ${}^{8}{Be}$ in the reaction of 126-MeV ${}^{12}C$ with ${}^{197}{Au}$

Erratum: Recoil effects in allowed nuclear beta decay

Erratum: Gamma-ray spectroscopy studies of ${}^{52}{Ti}$

Determination of the effective ${}^{12}C$ + ${}^{12}C$ potential from the sub-Coulomb single-particle resonances

Isospin-forbidden alpha decay of the 15.11-MeV state in ${}^{12}C$

Distortion effects in $α + α$ system

States in ${}^{29}P$ via the ${}^{32}S (p, α) {}^{29}P$ reaction

Lifetimes of the ${(f_{\frac{7}{2}})}^{3} {\frac{15}{2}}^{-}$ states in ${}^{51}V$ and ${}^{43}{Ca}$ and ${(f_{\frac{7}{2}})}^{2} 4^{+}$ states in ${}^{50}{Ti}$ and ${}^{42}{Ca}$ via heavy-ion recoil-distance-method measurements

Energy-dependent-core model for attenuation effects in quasifree scattering

Relativistic wave functions for pion-nucleon and pion-nucleus scattering

Energy dependence of two-nucleon transfer reactions on light nuclei

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