Recent Articles

Boson representation for the quantized rotator

E. R. Marshalek

Phys. Rev. C 11, 1426 (1975) - Published 1 April, 1975

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Semimicroscopic description of odd At isotopes

V. Paar

Phys. Rev. C 11, 1432 (1975) - Published 1 April, 1975

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The properties of odd At isotopes have been described by coupling three valence-shell protons to the quadrupole vibrational field. Qualitative and quantitative results have been compared with recent experimental data from the Dubna and Stockholm groups. It is interesting to note that two lowest $\frac{7}{2^{-}}$ states exchange their character in At nuclei away from the $N = 126$ shell closure. This pronounced feature of At isotopes is a combined effect of the particle-vibration coupling and the Pauli principle.

NUCLEAR STRUCTURE ${}^{203 - 211}{At}$ ; calculated spectra, electromagnetic properties. Three valence-shell particles coupled to quadrupole vibration.

Accuracy of the unitary pole approximation at positive energies for local potentials containing a hard core

A. V. Lagu, C. Maheshwari, and V. S. Mathur

Phys. Rev. C 11, 1443 (1975) - Published 1 April, 1975

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The accuracy of the unitary pole approximation (UPA) to the two-body $t$ matrix at positive energies has been examined for the case of a local potential with a hard core. To this effect the $S$ -wave phase shifts and the half-shell functions (Baranger, Giraud, Mukhopadhyaya, and Sauer) have been calculated for the Herzfeld potential as well as for its UPA. The agreement between the two sets, though satisfactory, is not as good as reported by Levinger and O'Donoghue, who did similar calculations for various singlet potentials. This result may be attributed to the existence of a bound-state pole in $t$ matrix in the negative energy region in the case of the Herzfeld potential.

NUCLEAR STRUCTURE Unitary pole approximation, hard core potential, positive energies.

Charge asymmetry effects and the trinucleon binding energy. II. Inclusion of the tensor force and singlet repulsion

B. F. Gibson and G. J. Stephenson, Jr.

Phys. Rev. C 11, 1448 (1975) - Published 1 April, 1975

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Calculations of the trinucleon binding energy using separable potentials having a tensor component in the triplet force and strong repulsion in the singlet force are reported. It is shown that the binding energy remains sensitive to the $N - N$ singlet effective range and that $| a_{nn} | < | a_{pp} |$ can be consistent with the ${}^{3}{He}$ Coulomb energy being less than the binding energy difference between ${}^{3}H$ and ${}^{3}{He}$ if one has $r_{nn} < r_{pp}$ . Sensitivity of the binding energy to other differences in the $N - N$ interactions is explored.

NUCLEAR STRUCTURE ${}^{3}H$ , ${}^{3}{He}$ , separable potential three-body calculation, tensor triplet, repulsive singlet, charge asymmetry.

Internal-conversion coefficient determination of odd parity for the 108.8-keV first-excited state of ${}^{91}{Rb}$

F. K. Wohn, W. L. Talbert, Jr., R. S. Weinbeck, M. D. Glascock, and J. K. Halbig

Phys. Rev. C 11, 1455 (1975) - Published 1 April, 1975

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Internal-conversion coefficients of the 108.8-keV transition in the decay of ${}^{91}{Kr}$ and the 93.6-keV transition in the decay of ${}^{91}{Rb}$ were measured by the electron-to- $γ$ -ray ratio method using a high-resolution magnetic spectrometer and by the x-ray-to- $γ$ -ray ratio method using a low-energy photon spectrometer. The 93.6-keV transition was found to be pure $E 2$ . The 108.8-keV transition from the first-excited state of ${}^{91}{Rb}$ was found to be pure $M 1$ , which determines the parity of this state as odd, as expected from spherical shell-model considerations, and contradicts a recently reported assignment of even parity for this state.

RADIOACTIVITY ${}^{91}{Kr}$ , ${}^{91}{Rb}$ [from ${}^{235}U (n, f)$ ]; measured $E$ and $I$ for low-energy ce's, x rays, $γ' s$ ; $π \sqrt{2}$ magnetic spectrometer, Ge(Li); deduced ICC, transition multipolarities; mass-separated $A = 91$ activity.

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Decay of the ${}^{10}{Be}$ $0^{+}$ 6.18-MeV level

P. Wagner, R. M. Freeman, A. Gallmann, and E. K. Warburton

Phys. Rev. C 11, 1459(R) (1975) - Published 1 April, 1975

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The relative branching ratios of the ${}^{10}{Be}$ 6.18-MeV level to the $1^{-}$ 5.96- and $2^{+}$ 3.37-MeV levels were measured via the ${}^{11}B (t, α γ) {}^{10}{Be}$ reaction. The results of (24±2)% and (76±2)%, respectively, are in agreement with a recent ${}^{9}{Be} (n, γ) {}^{10}{Be}$ experiment and in disagreement with the previous ${}^{9}{Be} (d, p γ) {}^{10}{Be}$ results.

NUCLEAR STRUCTURE ${}^{10}{Be}$ ; measured $γ$ -ray branching ratios 6.18-MeV level.

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Gamma-ray studies at the 2876- and 2879-keV resonances in ${}^{27}{Al}$ + $p$

G. F. Neal and P. R. Chagnon

Phys. Rev. C 11, 1461(R) (1975) - Published 1 April, 1975

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The $6^{-}$ assignment to the 14.358-MeV level of ${}^{28}{Si}$ and the concomitant $M 1$ character of the 14.358→11.577-MeV transition have been made rigorous by a linear-polarization measurement of this radiation at the 2876-keV resonance in ${}^{27}{Al}$ + $p$ . The spin and parity of the 2879-keV resonance, $E_{x} = 14.361$ MeV, are restricted to $2^{+}$ , 5, or $6^{+}$ , with $2^{+}$ preferred.

NUCLEAR REACTIONS ${}^{27}{Al} (p, γ)$ , ${}^{27}{Al} (p, α γ)$ , $E = 2.876, 2.879$ MeV. Measured $γ (θ)$ , linear polarization. ${}^{28}{Si}$ deduced $J^{π}$ , multipolarity.

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${}^{14}C (p, α) {}^{11}B$ reaction for $4 MeV < E_{p} < 7.5 MeV$

H. R. Weller, R. A. Blue, J. J. Ramirez, and E. M. Bernstein

Phys. Rev. C 11, 1464(R) (1975) - Published 1 April, 1975

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The ${}^{14}C (p, α_{0}) {}^{11}B$ cross sections are presented for $4 MeV < E_{p} < 7.5 MeV$ . Probable spin assignments based on Legendre polynomial fits to the measured angular distributions are given and compared to the ${}^{14}C (p, p) {}^{14}C$ results.

NUCLEAR REACTIONS ${}^{14}C (p, α) {}^{11}B$ ; measured $σ (θ)$ , $E = 4.0 - 7.5$ MeV. Probable spin assignments deduced for ${}^{15}N$ levels. Compared results with those from ${}^{14}C (p, p) {}^{14}C$ experiment.

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Lifetime of the 3.830-MeV state of ${}^{41}{Ca}$

H. J. Kim, R. L. Robinson, and W. T. Milner

Phys. Rev. C 11, 1468(R) (1975) - Published 1 April, 1975

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The mean lifetime of the 3.830-MeV state of ${}^{41}{Ca}$ was determined from the delayed coincidence measurements between neutrons and $γ$ rays from the ${}^{28}{Si} ({}^{16}O, 2 p n γ) {}^{41}{Ca}$ reaction at 40-MeV incident energy using the direct timing method. The value of 4.16±0.20 nsec obtained is smaller but consistent with the "plunger" values previously reported.

NUCLEAR REACTIONS ${}^{28}{Si} ({}^{26}O, 2 p n γ)$ , $E = 40$ MeV. Measured lifetime of 3.830-MeV state.

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Masses of ${}^{74}{Br}$ and ${}^{76}{Br}$

D. H. Lueders, J. M. Daley, S. G. Buccino, F. E. Durham, C. E. Hollandsworth, W. P. Bucher, and H. D. Jones

Phys. Rev. C 11, 1470(R) (1975) - Published 1 April, 1975

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Threshold energies for the ${}^{74}{Se} (p, n) {}^{74}{Br}$ and ${}^{76}{Se} (p, n) {}^{76}{Br}$ reactions were obtained from excitation functions of low lying excited levels in ${}^{74, 76}{Br}$ and the first excited level in ${}^{74}{Se}$ . The ground state threshold results of 7.805 ± 0.015 and 5.815 ± 0.015 MeV, respectively, yield mass excesses of -65.302 ± 0.015 MeV for ${}^{74}{Br}$ and -70.303 ± 0.015 MeV for ${}^{76}{Br}$ . Results are compared to published values which are in error by 100-180 keV.

NUCLEAR REACTIONS ${}^{74, 76}{Se} (p, n γ) {}^{74, 76}{Br}$ , $E = 5.8 - 8.5$ MeV; measured $γ$ ray yields, prompt and delayed; deduced $Q$ , ${}^{74, 76}{Br}$ deduced mass excess. Enriched targets; Ge(Li) detector.

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Resonating-group study and importance of exchange processes in $N$ + ${}^{16}O$ scattering

D. R. Thompson and Y. C. Tang

Phys. Rev. C 11, 1473(R) (1975) - Published 1 April, 1975

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The scattering of nucleons by ${}^{16}O$ is studied with the resonating-group method and a generator-coordinate technique. The result shows that, at relatively high energies, the knockout process contributes significantly to the scattering amplitude, while the pickup process is of minor importance.

NUCLEAR REACTIONS ${}^{16}O (p, p)$ , $E = 37.4$ MeV; calculated $σ (θ)$ and $P (θ)$ . Resonating-group method with generator-coordinate technique.

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Thermal neutron capture gamma rays from neutron capture in ${}^{59}{Ni}$ and ${}^{63}{Ni}$

W. M. Wilson, G. E. Thomas, and H. E. Jackson

Phys. Rev. C 11, 1477(R) (1975) - Published 1 April, 1975

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The thermal neutron capture $γ$ -ray spectra for ${}^{60}{Ni}$ and ${}^{64}{Ni}$ have been observed from a sample previously irradiated to produce long-lived isotopes of ${}^{59}{Ni}$ and ${}^{63}{Ni}$ . New values of the neutron binding energy have been obtained for the compound systems ${}^{59}{Ni}$ , ${}^{60}{Ni}$ , ${}^{61}{Ni}$ , ${}^{62}{Ni}$ , and ${}^{64}{Ni}$ . The $γ$ -ray spectra for neutron capture by ${}^{59}{Ni}$ and ${}^{63}{Ni}$ are not as strongly peaked at high energies as the $γ$ -ray spectra observed for neutron capture by the even-mass target nuclei in the $A \approx 40 - 64$ mass region.

NUCLEAR REACTIONS ${}^{58}{Ni}$ , ${}^{59}{Ni}$ , ${}^{60}{Ni}$ , ${}^{61}{Ni}$ , ${}^{63}{Ni} (n, γ)$ ; $E_{n} = thermal$ ; measured $E_{γ}$ , $I_{γ}$ ; deduced binding energies, energy levels for ${}^{59}{Ni}$ , ${}^{60}{Ni}$ , ${}^{61}{Ni}$ , ${}^{62}{Ni}$ , ${}^{64}{Ni}$ . Irradiated natural target.

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Giant multipole resonances and the three-fluid hydrodynamical model of nuclei

L. C. Biedenharn, M. Trivedi, and Michael Danos

Phys. Rev. C 11, 1482(R) (1975) - Published 1 April, 1975

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The recently observed resonance at ∼ 11 MeV in ${}^{208}{Pb}$ is interpreted as the miniature quadrupole resonance (associated with the giant quadrupole resonance at 22 MeV) implied by the three-fluid hydrodynamical model. A difficulty arises with the miniature dipole resonance; this may signify that the simple hydrodynamic model has reached the limits of its validity. A numerical error in a previous publication is corrected.

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Calculation of parity mixing in ${}^{19}F$

M. Gari, A. H. Huffman, J. B. McGrory, and R. Offermann

Phys. Rev. C 11, 1485(R) (1975) - Published 1 April, 1975

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The conventional model of weak interactions is tested in the case of the recently measured $γ$ asymmetry in ${}^{19}F$ . It is shown that the conventional model leads to an asymmetry $δ$ about one-fourth to one-third of the experimental value. Extra currents in the hadronic part of the weak interaction could be an explanation for this discrepancy.

RADIOACTIVITY Parity violating $γ$ -decay calculation.

Erratum: Electromagnetic properties of the ${\frac{11}{2}}^{-}$ states in ${}^{111}{Sn}$ and ${}^{113}{Sn}$

R. Brenn, S. K. Bhattacherjee, G. D. Sprouse, and L. E. Young

Phys. Rev. C 11, 1488 (1975) - Published 1 April, 1975

$E 1$ transitions in ${}^{17}F$ . II. The region of the giant resonances

M. N. Harakeh, P. Paul, and Ph. Gorodetzky

Phys. Rev. C 11, 1008 (1975) - Published 1 March, 1975

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The giant dipole resonance of ${}^{17}F$ was studied by radiative proton capture. An observed integrated strength of 10 MeV mb, presumably mostly $T = \frac{1}{2}$ , is centered at 22 MeV with a width of ~ 5 MeV. Calculations were performed for odd-parity 2p-1h, 1p excitations in a basis of good isospin. These calculations predict correctly the observed strength distribution. Some general rules for the $T$ components of the $E 1$ collective state are consistent with the microscopic calculation. The $f_{\frac{7}{2}} \to d_{\frac{5}{2}}$ strength was located near 18 MeV, in agreement with other experimental evidence.

NUCLEAR REACTIONS ${}^{17}F$ , ${}^{16}O (p, γ)$ , $E_{p} = 15.75 - 31.66$ MeV. Measured $\frac{d σ}{d Ω} (90 °)$ . Measured angular distributions deduced $E_{T = \frac{1}{2}}$ of GDR. Calculated $1 p$ and 2p-1h states of ${}^{17}F$ . Compared with experimental results.

Application of the generalized semimicroscopic model to $1 f_{\frac{7}{2}}$ nuclei

S. M. Abecasis, Carlos A. Heras, and F. Krmpotić

Phys. Rev. C 11, 1015 (1975) - Published 1 March, 1975

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A detailed description with the generalized semimicroscopic model of the properties of the low-lying states of ${}^{49}{Ti}$ , ${}^{51}{Cr}$ , and ${}^{57}{Co}$ is performed. The last one is taken as a typical and well-known representative of the odd-mass cobalt isotopes. Calculated energy-level sequence, electromagnetic properties, spectroscopic factors, and lifetimes compare favorably with experiment.

NUCLEAR STRUCTURE ${}^{49}T$ , ${}^{51}{Cr}$ , and ${}^{57}{Co}$ ; calculated levels, $J$ , $π$ , $S$ , $q$ , $μ$ , $B (E 2)$ , $B (M 1)$ , $δ$ , $b$ , and $τ$ . Generalized semimicroscopic model.

Density-matrix expansion for an effective nuclear Hamiltonian. II

J. W. Negele and D. Vautherin

Phys. Rev. C 11, 1031 (1975) - Published 1 March, 1975

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The density matrix expansion (DME) was originally introduced to establish contact between microscopic many-body theory based on a realistic two-body interaction and simplified phenomenological interactions of the Skyrme type. As a result of subsequent applications of the DME and simple phenomenological forces to deformed nuclei and problems in nuclear collective motion, several extensions to the original work are presented. The surface energy coefficient is shown to be -19.06 MeV when the spin-orbit and starting energy contributions are included, yielding excellent agreement with the semiempirical mass formula value of -18.56. The dominant effects of finite range are shown to be straightforwardly included in the direct Hartree term, and the Pauli operator is expressed in terms of the density matrix, yielding new insight into the local density approximation. Detailed comparisons are presented with Skyrme forces, and the density of states at the Fermi surface is shown to be reasonably well reproduced with the DME.

Low-energy levels and gamma transitions in ${}^{58}{Co}$

B. J. Brunner, R. G. Arns, S. E. Caldwell, C. M. Rozsa, J. W. Smith, and S. W. Sprague

Phys. Rev. C 11, 1042 (1975) - Published 1 March, 1975

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The mean lifetimes of eight excited states in ${}^{58}{Co}$ have been measured by the Doppler-shift-attenuation method using the reaction ${}^{55}{Mn} (α, n γ) {}^{58}{Co}$ at $E_{α} = 9.5$ MeV. $γ$ rays were detected at 30 and 150° to the beam axis in a 38.5 ${cm}^{3}$ Ge(Li) detector. The following mean lifetimes were measured ( $τ$ in ps): $τ (366 keV level) = {1.70}_{- 0.60}^{+ 1.00}$ , $τ (347) = {2.10}_{- 0.70}^{+ 1.30}$ , $τ (457) = {1.25}_{- 0.38}^{+ 0.45}$ , $τ (886) = {0.25}_{- 0.07}^{+ 0.11}$ , $τ (1184) = {0.24}_{- 0.07}^{+ 0.12}$ , $τ (1354) = {0.90}_{- 0.52}^{+ 2.00}$ , $τ (1378) = {0.23}_{- 0.08}^{+ 0.13}$ , $τ (1435) = {0.87}_{- 0.50}^{+ 3.00}$ . Angular distributions of six $γ$ rays were measured using the reaction ${}^{58}{Fe} (p, n γ) {}^{58}{Co}$ at $E_{p} = 3.33 - 4.73$ MeV. The results were compared with Hauser-Feshbach calculations and the following spin assignments were made: 112 keV level, $3^{+}$ ; 366 keV, $3^{+}$ ; 374 keV, $5^{+}$ ; 457 keV, $4^{+}$ ; 1040 keV, $3^{+}$ ; 1435 keV, $1^{+}$ ${(0, 2, 3)}^{+}$ .

NUCLEAR STRUCTURE ${}^{55}{Mn} (α, n γ)$ , $E = 9.5$ MeV; measured Doppler shifts, deduced lifetimes; ${}^{58}{Fe} (p, n γ)$ , $E = 3.33 - 4.73$ MeV; measured angular distributions, deduced $J$ and $δ$ .

Consequences of nuclear dynamics for the nonrelativistic $π NN$ vertex

J. M. Eisenberg, J. V. Noble, and H. J. Weber

Phys. Rev. C 11, 1048 (1975) - Published 1 March, 1975

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Boson representation for the quantized rotator

Semimicroscopic description of odd At isotopes

Accuracy of the unitary pole approximation at positive energies for local potentials containing a hard core

Charge asymmetry effects and the trinucleon binding energy. II. Inclusion of the tensor force and singlet repulsion

Internal-conversion coefficient determination of odd parity for the 108.8-keV first-excited state of ${}^{91}{Rb}$

Decay of the ${}^{10}{Be}$ $0^{+}$ 6.18-MeV level

Gamma-ray studies at the 2876- and 2879-keV resonances in ${}^{27}{Al}$ + $p$

${}^{14}C (p, α) {}^{11}B$ reaction for $4 MeV < E_{p} < 7.5 MeV$

Lifetime of the 3.830-MeV state of ${}^{41}{Ca}$

Masses of ${}^{74}{Br}$ and ${}^{76}{Br}$

Resonating-group study and importance of exchange processes in $N$ + ${}^{16}O$ scattering

Thermal neutron capture gamma rays from neutron capture in ${}^{59}{Ni}$ and ${}^{63}{Ni}$

Giant multipole resonances and the three-fluid hydrodynamical model of nuclei

Calculation of parity mixing in ${}^{19}F$

Erratum: Electromagnetic properties of the ${\frac{11}{2}}^{-}$ states in ${}^{111}{Sn}$ and ${}^{113}{Sn}$

$E 1$ transitions in ${}^{17}F$ . II. The region of the giant resonances

Application of the generalized semimicroscopic model to $1 f_{\frac{7}{2}}$ nuclei

Density-matrix expansion for an effective nuclear Hamiltonian. II

Low-energy levels and gamma transitions in ${}^{58}{Co}$

Consequences of nuclear dynamics for the nonrelativistic $π NN$ vertex

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