Recent Articles

Effect of rearrangement on the single-particle field of ${}^{16}O$

B. Rouben, R. Padjen, and G. Saunier

Phys. Rev. C 10, 2561 (1974) - Published 1 December, 1974

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Both the third-order and the second-order rearrangemetn corrections are included in a self-consistent calculation of the single-particle field of ${}^{16}O$ , carried out with a model $G$ matrix derived from the soft-core Sprung-de-Tourreil interaction. Saturation is improved: The charge radius increases by 7% and the central nuclear density is diminished by 10%. For the interaction chosen, the effect of the second-order (energy-dependent) corrections are larger than those of the third order. The self-consistent "single-particle" energies in the nucleus, and the single-particle wave functions, are used to calculate the removal energies of single particles, the results being in quite good agreement with experiment.

NUCLEAR STRUCTURE ${}^{16}O$ ; calculated radius, single-particle separation energies, total binding energy. Propagator renormalization self-consistent method.

Projected band-mixed spectra of Fe and Ni isotopes

Jyoti K. Parikh

Phys. Rev. C 10, 2568 (1974) - Published 1 December, 1974

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The nuclear spectra of ${}^{54, 56, 58}{Fe}$ and ${}^{58, 60, 62}{Ni}$ are obtained by mixing various bands. The bands for each nucleus are obtained by considering the prolate and oblate Hartree-Fock solutions. The third band is obtained by considering two-particle-two-hole excitations on whichever is the lower solution of the above two. The states with definite angular momenta are projected and the orthogonalization is carried out to obtain the nuclear spectra. The Yukawa-Rosenfeld interaction (YR) and the Kuo-Brown interaction modified by McGrory et al. (KM) are used as the two-body interactions. The single particle energies are varied for each mucleus to give a good fit. A comparison between the interactions shows that the KM interaction for the Fe isotopes and the YR interaction for the Ni isotopes give better results. In general, the agreement with the experimental spectra is very good. However, the second $2^{+}$ state in ${}^{56, 58}{Fe}$ and ${}^{60}{Ni}$ cannot be explained by this model which considers only $K = 0$ bands. The high spin states have also been obtained. The effects of the band mixing on the nuclear spectra are discussed in detail for each nucleus.

NUCLEAR STRUCTURE ${}^{54, 56, 58}{Fe}$ , ${}^{58, 60, 62}{Ni}$ calculated energy levels. Projected Hartree-Fock method, band mixing.

Analog resonances and possible $T_{>}$ mixing in ${}^{77}{Br}$

J. W. Gray and J. C. Legg

Phys. Rev. C 10, 2577 (1974) - Published 1 December, 1974

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The locations and widths of several analog resonances in ${}^{77}{Br}$ have been measured. Comparison of resonance spectroscopic factors to stripping spectroscopic factors show poor agreement, but spectroscopic factor ratios for states of the same spin and parity show good agreement except for the $s$ -wave resonances. It is suggested that this disagreement may be explained by a mechanism of $T_{>}$ mixing between $\frac{1}{2} +$ resonances.

NUCLEAR REACTIONS ${}^{76}{Se} (p, p)$ , $E = 3.1 - 4.5$ MeV; measured $σ (E)$ ; deduced IAS, $Γ$ , $S$ . ${}^{76}{Se} (p, p^{'})$ , $E = 4.1 - 4.3$ MeV; measured $σ (E)$ .

Nuclear matter results for the Feshbach-Lomon interaction

Earle L. Lomon

Phys. Rev. C 10, 2584 (1974) - Published 1 December, 1974

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It is shown that the internal boundary condition (of the Feshbach-Lomon interaction), which has no effect on the two nucleon wave function, has a large effect on the saturation properties of nuclear matter. The binding energy per particle is altered over a range of approximately 30 MeV. The saturation density can be varied while the binding energy is kept fixed by correlated changes of the spin-spin, tensor, and central parts of the internal boundary condition. In this way the nuclear parameters are fitted without altering the good fit of the Feshbach-Lomon interaction to the two body data. The nuclear matter calculation is performed by matrix inversion of a Bethe-Goldstone equation which has been suitably modified to impose the external and internal boundary conditions. A self-consistent hole spectrum is used. A free particle spectrum is used for most of the results. The effect of a single particle potential of the strength that would cancel three-body cluster contributions is investigated, and found to be of marginal importance for the boundary condition type interaction, and insensitive to the potential strength. Best nuclear matter internal parameters are close to the $S$ -state pair superfluidity threshold, implying pairing effects in the nuclear surface and neutron stars.

Renormalized Brueckner-Hartree-Fock and density dependent Hartree-Fock theories of finite nuclei

K. T. R. Davies, R. J. McCarthy, J. W. Negele, and P. U. Sauer

Phys. Rev. C 10, 2607 (1974) - Published 1 December, 1974

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Renormalized Brueckner-Hartree-Fock and density dependent Hartree-Fock calculations in the literature have been difficult to compare because they involve both different physical approximations and also technical computational differences. Hence, results obtained in both calculations for ${}^{40}{Ca}$ are corrected for technical differences and compared in detail. It is shown that comparable Brueckner-Hartree-Fock calculations using an oscillator basis and using the local density approximation are in good numerical agreement, and that three mechanisms are of roughly equal importance in obtaining the proper interior density: occupation probabilities, the potential arising from the variation of the pauli operator, and the phenomenological parametrization of higher order corrections to the effective nuclear interaction. The renormalized oscillator basis calculations include only the effect of occupation probability diagrams. The "bare" local density approximation results are an improvement over the renormalized results since the former includes the effects of both occupation probabilities and the variation of the Pauli operator. The adjusted local density approximation calculations then give further improvement due to the phenomenological parametrization of the force, simulating the effect of higher-order diagrams.

NUCLEAR STRUCTURE Renormalized Brueckner-Hartree-Fock and density dependent Hartree-Fock theory. Application to ${}^{40}{Ca}$ .

Study of the reaction ${}^{12}C ({}^{12}C, d) {}^{22}{Na}$

G. KeKelis and J. D. Fox

Phys. Rev. C 10, 2613 (1974) - Published 1 December, 1974

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Excitation functions for the reaction ${}^{12}C ({}^{12}C, d) {}^{22}{Na}$ in the energy range 37-44 MeV (lab) are compared to those for the ${}^{12}C ({}^{12}C, p) {}^{23}{Na}$ reaction. Evidence is presented that the different channels "resonate" at different energies.

NUCLEAR REACTIONS ${}^{12}C ({}^{12}C, d)$ , ${}^{12}C ({}^{12}C, p)$ . Measured $σ (E_{d})$ , $σ (E_{p})$ , for $θ = 0 °$ , $E ({}^{12}C) = 37 - 44$ MeV.

Empirical relation between the energy of the topmost particle and the mean binding energy of nuclei

Minoru Harada

Phys. Rev. C 10, 2616 (1974) - Published 1 December, 1974

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On the basis of experimental knowledge, it is shown that separation energy thresholds cannot be interpreted as experimental single-particle energies, and that the energy of the topmost particle in conventional nuclear single-particle potentials is smaller in absolute magnitude than the mean binding energy. Connections with Hugenholtz and Van Hove's theorem are briefly discussed.

Pion photoproduction on ${}^{6}{Li}$ near threshold

J. H. Koch and T. W. Donnelly

Phys. Rev. C 10, 2618 (1974) - Published 1 December, 1974

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We present the results of an improved calculation of pion photoproduction on ${}^{6}{Li}$ near threshold and compare with the recent data of Deutsch et al. The theoretical cross sections are found to be about 60% higher than the experimental values.

NUCLEAR REACTIONS ${}^{6}{Li} (γ, π) {}^{6}{He}$ , calculated $σ (E)$ near threshold.

Limitation on complete fusion during heavy-ion collisions

D. Glas and U. Mosel

Phys. Rev. C 10, 2620 (1974) - Published 1 December, 1974

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In a recent paper Lefort and collaborators have extracted a critical distance of approach as the mechanism limiting fusion of two heavy ions. In this comment it is shown that this analysis does not depend on the specific model used for the calculation of the ion-ion potential. Furthermore an expression is derived to analyze both high- and low-energy fusion data on the same basis. It is concluded that all existing data are compatible with the existence of a critical distance. However, data spanning a larger range of energies and being more accurate at high energies are needed for a final check of the critical distance hypothesis.

NUCLEAR REACTIONS Heavy-ion complete fusion; critical distance of approach.

Distorted-wave theory of multistep processes

N. Austern and C. M. Vincent

Phys. Rev. C 10, 2623 (1974) - Published 1 December, 1974

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Distorted-wave theory of multistep processes: A reply

D. Robson

Phys. Rev. C 10, 2626 (1974) - Published 1 December, 1974

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Correlation between the ( $d, γ_{0}$ ) and ( $p, γ_{0}$ ) cross sections in the giant dipole resonance of ${}^{16}O$

M. Danos and H. R. Weller

Phys. Rev. C 10, 2627(R) (1974) - Published 1 December, 1974

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The reaction theory of Fano is applied to the analysis of the ${}^{15}N (p, γ_{0}) {}^{16}O$ data vis à vis the ${}^{14}N (d, γ_{0}) {}^{16}O$ data. The result is consistent with the Gillet model which attributes the structure near 22.9 MeV in ${}^{16}O$ to a 2p-2h quasibound state.

NUCLEAR STRUCTURE ${}^{16}O$ ; extracted resonance energy of quasibound state from ${}^{15}N (p, γ) {}^{16}O$ data. Compared to Gillet's model.

RAPID COMMUNICATION

Excitation energy of the second excited state of ${}^{12}C$

P. L. Jolivette, J. D. Goss, A. A. Rollefson, and C. P. Browne

Phys. Rev. C 10, 2629(R) (1974) - Published 1 December, 1974

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RAPID COMMUNICATION

Decay of ${}^{133}{Xe}^{g}$

L. M. Cavallo, F. J. Schima, and M. P. Unterweger

Phys. Rev. C 10, 2631(R) (1974) - Published 1 December, 1974

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The half-life of isotopically separated ${}^{133}{Xe}^{g}$ was determined by measurement in a $4 π γ$ pressure ionization chamber. The value obtained was 5.245 days with an uncertainty of 0.006 days which is the linear sum of the standard error at the 99% confidence limit and the estimated systematic errors. This result was confirmed by two separate half-life measurements employing a Ge(Li) detector. The $γ$ rays which deexcite the level at 383 keV in ${}^{133}{Cs}$ have been observed. The intensities of the 383- and 221-keV $γ$ rays relative to the 302-keV $γ$ ray intensity were found to be 0.489 and 0.020 with the respective standard errors calculated to be 3.8% and 40%.

RADIOACTIVITY ${}^{133}{Xe}^{g}$ , measured $T_{\frac{1}{2}}$ , $γ$ relative intensity. Enriched source, $4 π γ$ pressure chamber, Ge(Li) detector.

RAPID COMMUNICATION

First excited $A = 9$ isospin quartet

W. Benenson and E. Kashy

Phys. Rev. C 10, 2633(R) (1974) - Published 1 December, 1974

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The first excited state of ${}^{9}C$ and its analog in ${}^{9}B$ have been observed, and their mass excesses and widths have been measured. This completes a new mass quartet which differs from the predictions of the isobaric multiple mass equation less significantly than the ground state $A = 9$ quartet.

NUCLEAR REACTIONS ${}^{12}C$ ( ${}^{3}{He}$ , ${}^{6}{He}$ ), $E = 74$ MeV measured $E_{x}$ of ${}^{9}C$ first excited state. ${}^{11}B (p, t)$ , $E = 46.5$ MeV, measured $E_{x}$ of second $T = \frac{3}{2}$ level in ${}^{9}B$ . Decuced coefficient of multiplet mass equation for first excited $A = 9$ quartet.

RAPID COMMUNICATION

Comparison of fragment kinetic energies from two ${}^{237}{Pu}$ fission isomers

S. L. Bacharach, P. S. Hoeper, J. A. Morrissey, and J. K. Temperley

Phys. Rev. C 10, 2636(R) (1974) - Published 1 December, 1974

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Fission fragment kinetic energy distributions have been measured separately for two spontaneously fissioning isomers of ${}^{237}{Pu}$ produced by the ${}^{237}{Np} (d, 2 n) {}^{237}{Pu}^{m}$ reaction at 13 MeV. Single fragment peak to valley ratios and heavy and light fragment peak positions were measured for each of the two isomers. Average fragment kinetic energies for each isomer were calculated and compared. Values of isomeric fission half-life are reported with increased accuracy.

NUCLEAR REACTIONS, FISSION ${}^{237}{Np} (d, 2 n) {}^{237}{Pu}^{m}$ , $E = 13$ MeV. Spontaneously fissioning isomers. For each isomer: fragment $E$ , $T_{\frac{1}{2}}$ .

RAPID COMMUNICATION

Removal of an apparent discrepancy of excitation energies of ${}^{55}{Co}$

J. D. Goss, P. L. Jolivette, A. A. Rollefson, and C. P. Browne

Phys. Rev. C 10, 2641(R) (1974) - Published 1 December, 1974

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RAPID COMMUNICATION

Lipkin-Nogami approximation of pairing interaction

W. Y. Ng and B. Castel

Phys. Rev. C 10, 2643(R) (1974) - Published 1 December, 1974

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RAPID COMMUNICATION

Nuclear charge form factor with intrinsic hyperspherical-coordinate wave functions

M. Sotona and J. Žofka

Phys. Rev. C 10, 2646(R) (1974) - Published 1 December, 1974

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A simple expression for the intrinsic form factor of magic nuclei in the lowest order approximation of the hyperspherical-coordinate method is derived, discussed, and applied to ${}^{16}O$ and ${}^{4}{He}$ . A good agreement with experimental values for $q^{2} ≲ 8$ ${fm}^{- 2}$ and the appearance of a dip in the form factor of ${}^{4}{He}$ are noticed.

NUCLEAR STRUCTURE ${}^{4}{He}$ , ${}^{16}O$ ; calculated intrinsic charge form factor. Lowest order hyperspherical-coordinate wave functions; comparison with experiment.

RAPID COMMUNICATION

Shell-model calculations for ${}^{51}{Ti}$ and ${}^{52}V$

C. C. Fu and M. L. Rustgi

Phys. Rev. C 10, 2649(R) (1974) - Published 1 December, 1974

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Employing ${}^{48}{Ca}$ as the core and the renormalized matrix elements of Kuo and Brown, the nuclear energy levels of ${}^{51}{Ti}$ and ${}^{52}V$ are calculated within the spherical shell-model frame-work. For ${}^{51}{Ti}$ all the $0 f - 1 p$ configurations are included but the ${}^{52}V$ nucleus is described within the ${(0 f_{\frac{7}{2}}, 1 p_{\frac{3}{2}})}^{3}_{p} \times {(1 p_{\frac{3}{2}}, 0 f_{\frac{5}{2}}, 1 p_{\frac{1}{2}})}^{1}_{n}$ configuration. The results are compared with experiment.

NUCLEAR STRUCTURE ${}^{51}{Ti}$ , ${}^{52}V$ ; calculated energy levels, spectroscopic factors for ${}^{50}{Ti} (d, p) {}^{51}{Ti}$ ; magnetic moment for ${}^{51}{Ti}$ .

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Recent Issues

Effect of rearrangement on the single-particle field of ${}^{16}O$

Projected band-mixed spectra of Fe and Ni isotopes

Analog resonances and possible $T_{>}$ mixing in ${}^{77}{Br}$

Nuclear matter results for the Feshbach-Lomon interaction

Renormalized Brueckner-Hartree-Fock and density dependent Hartree-Fock theories of finite nuclei

Study of the reaction ${}^{12}C ({}^{12}C, d) {}^{22}{Na}$

Empirical relation between the energy of the topmost particle and the mean binding energy of nuclei

Pion photoproduction on ${}^{6}{Li}$ near threshold

Limitation on complete fusion during heavy-ion collisions

Distorted-wave theory of multistep processes

Distorted-wave theory of multistep processes: A reply

Correlation between the ( $d, γ_{0}$ ) and ( $p, γ_{0}$ ) cross sections in the giant dipole resonance of ${}^{16}O$

Excitation energy of the second excited state of ${}^{12}C$

Decay of ${}^{133}{Xe}^{g}$

First excited $A = 9$ isospin quartet

Comparison of fragment kinetic energies from two ${}^{237}{Pu}$ fission isomers

Removal of an apparent discrepancy of excitation energies of ${}^{55}{Co}$

Lipkin-Nogami approximation of pairing interaction

Nuclear charge form factor with intrinsic hyperspherical-coordinate wave functions

Shell-model calculations for ${}^{51}{Ti}$ and ${}^{52}V$

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