Recent Articles

Proton-neutron hole states in Sb isotopes populated in $β^{-}$ decay of ${}^{128}{Sn}$

Lewis L. Nunnelley and W. Loveland

Phys. Rev. C 13, 2017 (1976) - Published 1 May, 1976

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The $γ$ rays and x rays following the $β^{-}$ decay of ${}^{128}{Sn}$ have been measured after chemical separation of this nucleus from ${}^{235}U$ fission products. A level scheme for the Sb daughter nucleus is proposed based upon the study of $γ$ -ray singles spectra, $γ - γ$ , $β^{-} - γ$ , and x-ray- $γ$ coincidence data. Internal conversion coefficients, $γ$ -ray transition intensities, and $log ft$ values were combined to deduce spins and parities. Hindrance of the $β^{-}$ decay of a $d_{\frac{3}{2}}$ neutron was partially accounted for by a core-polarization model.

RADIOACTIVITY ${}^{128}{Sn}$ , measured $E_{γ}$ , $I_{γ}$ , $E_{β}$ , $β γ$ coin, $γ γ$ coin, $x γ$ coin; deduced $log ft$ , $Q$ , ${}^{128}{Sb}$ deduced levels, $J$ , $π$ , ICC. Chemically separated ${}^{235}U$ fission products.

Radioactive decay of 47-min ${}^{154}{Eu}^{m}$ %

William H. Zoller, William B. Walters, Patrick W. Gallagher, and Richard A. Meyer

Phys. Rev. C 13, 2024 (1976) - Published 1 May, 1976

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A 47-min isomer has been identified in ${}^{154}{Eu}$ . Sources were prepared in ( $n, γ$ ) and ( $d, p$ ), ( $d, 2 n$ ) and ( $p, n$ ), and ( $d, α$ ) reactions on Eu, Sm, and Gd, respectively, and in each case the 47-min activity followed the Eu fraction in the separation of ${EuSO}_{4}$ . Singles and coincidence $γ$ -ray studies confirmed a number of the observed $γ$ rays in a structure consistent with capture $γ$ -ray studies. Owing to the high conversion coefficients for low energy $γ$ rays a complete decay scheme has not been confirmed for ${}^{154}{Eu}^{m}$ .

RADIOACTIVITY ${}^{154}{Eu}^{m}$ ; measured $T_{\frac{1}{2}}$ , $E_{γ}$ , $I_{γ}$ , $γ γ$ coin, deduced levels, $J$ , $π$ . Enriched targets. Ge(Li) and Si(Li) detectors, 170 eV at 5.9 keV.

Measurement of the radiative branching ratio for the 7.65-MeV state in ${}^{12}C$ using the cascade gamma decays

A. W. Obst and W. J. Braithwaite

Phys. Rev. C 13, 2033 (1976) - Published 1 May, 1976

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A measurement of the cascade $γ$ radiation from the 7.65-MeV $J^{π} = 0^{+}$ state in ${}^{12}C$ is reported. The cascade $γ$ radiation through the 4.44-MeV $J^{π} = 2^{+}$ state in ${}^{12}C$ is responsible for 98% of stellar ${}^{12}C$ production, the remaining 2% proceeding by $E 0$ pair decay. The two $E 2$ $γ$ rays were measured in coincidence with inelastically scattered protons which resonantly populated the 7.65-MeV state at $E_{p} = 10.48$ MeV. A high efficiency detection system was used, consisting of four 12.5-cm × 12.5-cm NaI $γ$ detectors and four silicon surface barrier particle counters. A value of (4.09 ± 0.29) × $10^{- 4}$ was obtained for the radiative branching ratio, in agreement with the larger of the two sets of values previously reported.

NUCLEAR STRUCTURE ${}^{12}C$ , 7.65 MeV state; measured $\frac{Γ_{γ}}{Γ}$ . Stellar helium burning.

Shell-model calculations for $A = 18$ nuclei with a finite charge-dependent potential

A. K. Deka and P. Mahanta

Phys. Rev. C 13, 2044 (1976) - Published 1 May, 1976

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Shell-model calculations of $T = 1$ isospin states of $A = 18$ nuclei have been performed with a realistic, finite, and charge-dependent potential. The charge dependence is found to influence the reduced integrals calculated by using the separation method and the reference spectrum method. The two-body matrix elements and the energy levels show good agreement with the results of other realistic potentials, particularly with those of the Hamada-Johnston potential. An estimate of the charge dependence of the potential is also made and compared with similar results.

NUCLEAR STRUCTURE Bethe-Goldstone equation, $T = 1$ isospin states, $A = 18$ nuclei, charge-dependent potential, RHEL.

Solution of the Bethe-Goldstone equation with the Sussex interaction

Paul Goldhammer

Phys. Rev. C 13, 2051 (1976) - Published 1 May, 1976

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An estimate of the possible error made by using second order perturbation theory with the Sussex interaction is obtained through solution of the Bethe-Goldstone equation. The correction is on the order of 1 MeV in the ${}^{3}S_{1}$ state. A much more modest correction is found for other partial waves. Particular attention must be paid to the method by which one includes the single particle insertions for the particle states in higher order.

NUCLEAR STRUCTURE Sussex interaction. Higher order effects.

Level structure of the odd- $A$ Rb istopes

K. Krishan, S. K. Basu, and S. Sen

Phys. Rev. C 13, 2055 (1976) - Published 1 May, 1976

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The odd- $A$ Rb isotopes ${}^{83}{Rb}$ and ${}^{85}{Rb}$ are studied in a semimicroscopic model which couples the proton quasiparticle motion in the $Z = 28 - 50$ shell to the quadrupole vibrations of the neighboring even core. The agreement between the calculated and experimental level spectra, spectroscopic factors, and electromagnetic transition rates is found to be satisfactory. The scope of further theoretical study is discussed in the light of recent experimental findings.

NUCLEAR STRUCTURE ${}^{83, 85}{Rb}$ ; calculated levels, $J$ , $π$ , $B (E 2)$ , $B (M 1)$ , $τ$ , $γ$ branching. Quasiparticle-phonon coupling.

Comment on " $E 1$ excitations in $A = 15$ nuclei"

H. R. Weller, N. R. Roberson, D. G. Rickel, C. P. Cameron, and R. D. Ledford

Phys. Rev. C 13, 2062 (1976) - Published 1 May, 1976

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RAPID COMMUNICATION

Odd parity levels in ${}^{133}{La}$ and the particle-plus-triaxial-rotor model

E. A. Henry and R. A. Meyer

Phys. Rev. C 13, 2063(R) (1976) - Published 1 May, 1976

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Odd parity levels in ${}^{133}{La}$ are studied by $β$ decay of mass separated 5.4-h ${}^{133}{Ce}$ . Good agreement between experiment and theory is found for level energies and transition probability ratios when the particle-plus-triaxial-rotor model is used.

RADIOACTIVITY ${}^{133}{Ce}$ ; measured $E γ$ , $I γ$ , $I_{ce}$ ; deduced $log ft$ . ${}^{133}{La}$ deduced levels, $J$ , $π$ , ICC, $Λ$ . Enriched targets, mass separation, Ge(Li) and Si(Li) detectors.

RAPID COMMUNICATION

Multipole mixing ratios of the single-neutron-hole transitions of ${}^{207}{Pb}$

F. T. Avignone, III and T. A. Girard

Phys. Rev. C 13, 2067(R) (1976) - Published 1 May, 1976

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Directional-correlation measurements have been made on the 1770-570 keV, 1442-897 keV, and 1063-570 keV, $γ$ -ray cascades of ${}^{207}{Pb}$ , using an automated rotating-detector Ge(Li)-NaI(Tl) coincidence spectrometer. The present results imply an $\frac{E 5}{M 4}$ multipole mixing ratio $δ (1063) = 0.016 (11)$ and $\frac{E 2}{M 1}$ mixing ratios $δ (1770) = + 0.082 (15)$ and $δ (897) = + 0.075 (25)$ . The values obtained by averaging these and previous results are $δ (1770) = + 0.087 (5)$ , $δ (1063) = + 0.020 (10)$ , and $δ (897) = + 0.089 (11)$ . When these values are compared to the single-neutron-hole calculations made in the oscillator basis with $ℏ ω = 7.6$ meV, the best over-all agreement is obtained for the neutron-hole effective charge $ε_{n} ≃ 0.89$ .

RADIOACTIVITY ${}^{207}{Bi}$ ; measured $γ γ (θ)$ ; deduced $δ$ for $γ$ rays in ${}^{207}{Pb}$ .

RAPID COMMUNICATION

Resonance absorption in the giant $M 1$ resonance region of ${}^{208}{Pb}$

Philip B. Smith

Phys. Rev. C 13, 2071(R) (1976) - Published 1 May, 1976

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A neutron unbound state lying at $E_{x} = 7685$ keV in ${}^{208}{Pb}$ , purportedly belonging to the giant $M 1$ resonance in this element, has been studied in resonance absorption with $γ$ rays from the $E_{p} = 1354$ -keV resonance in the ${}^{34}S (p, γ) {}^{35}{Cl}$ reaction. The absorber was 3-cm natural lead. The tungsten collimator subtended a (geometrical) half angle of 0.77° at the target. The absorption dip was fitted with a five-parameter Lorentz curve. The level parameters found are $E_{n} = 316.0 \pm 0.8$ keV, $Γ_{t} = {1.1}_{- 0.3}^{+ 0.5}$ keV, and $Γ_{γ 0} = 14_{- 4}^{+ 6}$ eV.

NUCLEAR REACTIONS ${}^{208}{Pb}$ , resonance absorption; $E_{x} = 7685$ keV; deduced $E_{n}$ , $Γ_{γ 0}$ , $Γ_{t}$ .

Isomers ${}^{84}Y^{m}$ and ${}^{85}{Zr}^{m}$

R. Iafigliola and J. K. P. Lee

Phys. Rev. C 13, 2075 (1976) - Published 1 May, 1976

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Two new isomers were identified: ${}^{84}Y^{m}$ ( $1^{+}$ ) decaying with a 4.6 ± 0.2 sec half-life and ${}^{85}{Zr}^{m}$ , decaying with a 10.9 ± 0.3 sec half-life. A 292.2 keV isomeric transition in ${}^{85}{Zr}$ was observed.

RADIOACTIVITY ${}^{84}Y^{(m)}$ from ${}^{84}{Sr} (p, n)$ , enriched target measured $E_{γ}$ , $I_{γ}$ , deduced $log ft$ . ${}^{85}{Zr}^{m}$ from ${}^{89}Y (p, 5 n)$ measured $E_{γ}$ , $I_{γ}$ . Ge(Li) detectors.

RAPID COMMUNICATION

Assignment of $0^{-}$ to the 2.99-MeV level in ${}^{38}K$ via the ${}^{40}{Ca} (d, α) {}^{38}K$ reaction

D. G. Rickel, N. R. Roberson, J. David Turner, H. R. Weller, and D. R. Tilley

Phys. Rev. C 13, 2077(R) (1976) - Published 1 May, 1976

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RAPID COMMUNICATION

Remeasurement of $p_{y}$ for the ${}^{2}H (d, \vec{n}) {}^{3}{He}$ reaction and its bearing on the reported $f$ -wave admixture of the lowest $2^{-}$ state in ${}^{4}{He}$

W. Tornow, S. E. Skubic, R. C. Byrd, P. W. Lisowski, and R. L. Walter

Phys. Rev. C 13, 2080(R) (1976) - Published 1 May, 1976

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The polarization of neutrons from the reaction ${}^{2}H (d, \vec{n}) {}^{3}{He}$ has been measured for a deuteron energy $E_{d} = 2.44$ MeV at emission angles of 45° and 55° (lab). The polarization values are discussed in relation both to previously reported discrepant data and to measured differences between $p_{y}$ and $A_{y}$ in the reaction ${}^{3}H (p, n) {}^{3}{He}$ .

NUCLEAR REACTIONS ${}^{2}H (d, \vec{n}) {}^{3}{He}$ , $E_{d} = 2.44$ MeV; measured neutron polarization $p_{y}$ .

RAPID COMMUNICATION

Resonance 2.7 eV above the ${}^{64}{Ni} (p, n_{1}) {}^{64}{Cu}^{*}$ threshold

H. W. Lefevre and E. W. Ross

Phys. Rev. C 13, 2083(R) (1976) - Published 1 May, 1976

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Time of flight spectra of near threshold neutrons from the ${}^{64}{Ni} (p, n_{1}) {}^{64}{Cu}^{*}$ reaction clearly show the presence of a ${\frac{5}{2}}^{+}$ resonance which is located 2.7 eV above the 2.67-MeV threshold. Its total width is 5 eV and its peak cross section is 14 mb. Through this study one deduces the basic limitation on the technique of high resolution spectroscopy very near reaction thresholds. Very near neutron thresholds, because a number of kinematic factors conspire in a favorable way, one can achieve the equivalent of slow-neutron resolution even though the neutrons are not slow. We know of no other technique which would allow individual study of such resonances.

NUCLEAR REACTIONS ${}^{64}{Ni} (p, n_{1}) {}^{64}{Cu}^{*}$ , near threshold; measured neutron spectra. Deduced resonance parameters of the first resonance above threshold. Deduced basic limitations on the near threshold technique.

RAPID COMMUNICATION

Vacuum polarization- and molecular-potential effects in heavy-ion scattering

Johann Rafelski

Phys. Rev. C 13, 2086(R) (1976) - Published 1 May, 1976

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The corrections to the heavy-ion scattering cross sections due to the presence of perturbing vacuum polarization and molecular potentials are evaluated. We find effects on the cross section up to 0.7% in ${}^{16}O$ with ${}^{208}{Pb}$ collisions due to vacuum polarization and up to 2.6% in U with Th collisions due to molecular and vacuum polarization corrections.

NUCLEAR REACTIONS Calculations of modifications of elastic heavy-ion $σ (θ)$ due to vacuum polarization and molecular potentials.

RAPID COMMUNICATION

$J^{π}$ assignment to the 4.841 MeV level in ${}^{208}{Pb}$

R. M. Del Vecchio, S. J. Freedman, G. T. Garvey, and M. A. Oothoudt

Phys. Rev. C 13, 2089(R) (1976) - Published 1 May, 1976

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A study of $γ$ rays in coincidence with inelastically scattered $α$ particles shows the level at 4.841 ± 0.005 MeV in ${}^{208}{Pb}$ to possess a large probability for decay to the ground state. The directional correlation of these $γ$ rays require that this level have $J^{π} = 1^{-}$ .

NUCLEAR REACTIONS ${}^{208}{Pb} (α, α^{'} γ)$ , $E_{α} = 35$ MeV; deduced $J^{π}$ of 4.841 MeV level.

Erratum: Why the Hauser-Feshbach formula works

P. A. Moldauer

Phys. Rev. C 13, 2093 (1976) - Published 1 May, 1976

$T = 2$ states in ${}^{12}C$ and ${}^{12}B$

D. Ashery, M. S. Zisman, G. W. Goth, G. J. Wozniak, R. B. Weisenmiller, and Joseph Cerny

Phys. Rev. C 13, 1345 (1976) - Published 1 April, 1976

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The ${}^{14}C (p, t) {}^{12}C$ and ${}^{14}C (p, {}^{3}{He}) {}^{12}B$ reactions have been investigated at $E_{p} = 54$ MeV. The lowest $0^{+}$ , $T = 2$ state in ${}^{12}C$ was identified at 27.57±0.03 MeV and a higher $T = 2$ state was found at 29.63±0.05 MeV. Their analogs in ${}^{12}B$ were found at 12.72±0.07 and 14.82±0.10 MeV, respectively. In a separate coincidence experiment, the proton and $α$ decay modes of the $T = 2$ states in ${}^{12}C$ were studied. The 27.57 MeV state decays (30±10)% by proton emission and less than 10% by $α$ emission. The 29.63 MeV state decays by about 80% proton emission and 20% $α$ emission.

NUCLEAR REACTIONS ${}^{14}C (p, t)$ , ( $p, {}^{3}{He}$ ), $E = 54$ MeV; measured $σ (θ)$ ; ${}^{12}C$ , ${}^{12}B$ levels, deduced $J$ , IAS. ${}^{14}C (p, t p)$ , ( $p, t α$ ), $E = 54$ MeV measured $pt$ coin, $p α$ coin.

Three-particle aspects in an $\frac{N}{D}$ approach to nuclear reactions

J. M. Greben and L. P. Kok

Phys. Rev. C 13, 1352 (1976) - Published 1 April, 1976

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Several approximations in a generalized $\frac{N}{D}$ approach to nuclear reactions are tested for the three-nucleon system. A detailed analysis of the analytic structure of the amplitudes for transitions between stable two-particle channels is presented. Three-particle unitarity is treated with a method which preserves the simple structure of the one variable $\frac{N}{D}$ equations. Calculations for the three-nucleon system are compared with the exact solutions of the Amado equations. The importance of exchange contributions to three-particle unitarity is stressed.

NUCLEAR REACTIONS Dispersion-relation method applied to the three-nucleon system. Analytic structure of scattering amplitudes. Three-particle unitarity.

Multistep inelastic processes in the reaction ${}^{28}{Si} ({}^{3}{He}, d) {}^{29}P$ leading to bound and unbound states

L. Ray and W. R. Coker

Phys. Rev. C 13, 1367 (1976) - Published 1 April, 1976

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We analyze the stripping reaction ${}^{28}{Si} ({}^{3}{He}, d) {}^{29}P$ at an incident ${}^{3}{He}$ energy of 35.3 MeV, considering seven residual states. These extend in excitation energy to 4.8 MeV with the highest four being unbound to proton emission and described via complex energy eigenstates. The results of a distorted-wave Born-approximation analysis are rather disappointing. Through a coupled-channel Born approximation analysis, inelastic excitation in both the entrance and exit channels is shown in several cases to be important in accounting for the detailed shape of the angular distributions. Additional data obtained at 20 and 40 MeV are included in the analysis as a check of the optical potentials and spectroscopic amplitudes adopted. The spectroscopic amplitudes used are consistent with results of large-basis shell-model calculations. Good fits to the ( ${}^{3}{He}, d$ ) data are obtained in both shape and magnitude, suggesting that the coupled-channel Born approximation should replace the distorted-wave Born approximation in the analysis of experimental data for single-nucleon transfer reactions in this mass region.

NUCLEAR REACTIONS ${}^{28}{Si} ({}^{3}{He}, d)$ , $E = 20, 35.3, 40$ MeV; DWBA and CCBA calculations of $σ (E_{d}, θ)$ . Deduced multistep inelastic contributions and spectroscopic amplitudes.

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Proton-neutron hole states in Sb isotopes populated in $β^{-}$ decay of ${}^{128}{Sn}$

Radioactive decay of 47-min ${}^{154}{Eu}^{m}$ %

Measurement of the radiative branching ratio for the 7.65-MeV state in ${}^{12}C$ using the cascade gamma decays

Shell-model calculations for $A = 18$ nuclei with a finite charge-dependent potential

Solution of the Bethe-Goldstone equation with the Sussex interaction

Level structure of the odd- $A$ Rb istopes

Comment on " $E 1$ excitations in $A = 15$ nuclei"

Odd parity levels in ${}^{133}{La}$ and the particle-plus-triaxial-rotor model

Multipole mixing ratios of the single-neutron-hole transitions of ${}^{207}{Pb}$

Resonance absorption in the giant $M 1$ resonance region of ${}^{208}{Pb}$

Isomers ${}^{84}Y^{m}$ and ${}^{85}{Zr}^{m}$

Assignment of $0^{-}$ to the 2.99-MeV level in ${}^{38}K$ via the ${}^{40}{Ca} (d, α) {}^{38}K$ reaction

Remeasurement of $p_{y}$ for the ${}^{2}H (d, \vec{n}) {}^{3}{He}$ reaction and its bearing on the reported $f$ -wave admixture of the lowest $2^{-}$ state in ${}^{4}{He}$

Resonance 2.7 eV above the ${}^{64}{Ni} (p, n_{1}) {}^{64}{Cu}^{*}$ threshold

Vacuum polarization- and molecular-potential effects in heavy-ion scattering

$J^{π}$ assignment to the 4.841 MeV level in ${}^{208}{Pb}$

Erratum: Why the Hauser-Feshbach formula works

$T = 2$ states in ${}^{12}C$ and ${}^{12}B$

Three-particle aspects in an $\frac{N}{D}$ approach to nuclear reactions

Multistep inelastic processes in the reaction ${}^{28}{Si} ({}^{3}{He}, d) {}^{29}P$ leading to bound and unbound states

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