Recent Articles

Identification of ${}^{184}{Hf}$

T. E. Ward, Y. Y. Chu, and J. B. Cumming

Phys. Rev. C 8, 340 (1973) - Published 1 July, 1973

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Hafnium-184 was identified as a product of the irradiations of natural tungsten and enriched ${}^{186}W$ with 92- and 200-MeV protons. The activity was produced by the ${}^{186}W (p, 3 p) {}^{184}{Hf}$ reaction. Mass-separated samples of ${}^{184}{Hf}$ were used to study its $β$ and $γ$ decay. Some $γ - γ$ and $β - γ$ coincidence measurements were performed. The following characteristics were observed: half-life, 4.12± 0.05 h; $β$ -ray end-point energies, 1100± 30, 850± 50, and 740± 30 keV; and $γ$ -ray energies, 41.4, 43.9, 47.9, 139.1, 181.0, and 344.9 keV. A decay scheme is proposed for ${}^{184}{Hf}$ based on the experimental data and theoretical predictions for the excited level structure of ${}^{184}{Ta}$ .

Studies of ${}^{205}{Bi}$ and ${}^{207}{Bi}$ by Proton-Transfer Reactions

Karl A. Erb and Walter S. Gray

Phys. Rev. C 8, 347 (1973) - Published 1 July, 1973

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The ( ${}^{3}{He}, d$ ) and ( $α, t$ ) reactions on ${}^{204}{Pb}$ and ${}^{206}{Pb}$ targets were investigated at bombarding energies of 44 and 45 MeV, respectively, in order to measure the fragmentation of the proton levels in ${}^{205}{Bi}$ and ${}^{207}{Bi}$ . Orbital angular momentum transfers and spectroscopic factors were determined for those bound states containing more than 5-10% of the active single-proton strengths. The fragmentation of the low-lying $1 h_{\frac{9}{2}}$ and $2 f_{\frac{7}{2}}$ proton orbitals was found to be consistent with qualitative particle-core expectations in both ${}^{205}{Bi}$ and ${}^{207}{Bi}$ , while the $1 f_{\frac{5}{2}}$ , $2 p_{\frac{3}{2}}$ , and $2 p_{\frac{1}{2}}$ strengths were distributed among a large number of levels. A level-by-level comparison between cross sections for the ( $α, t$ ) and ( ${}^{3}{He}, d$ ) reactions identified two high- $l$ transitions to levels near 2.6 MeV in both isotopes. These observations suggest the presence of interactions between members of the ( $3^{-}, h_{\frac{9}{2}}$ ) multiplet and at least one single-particle level from the next major shell as predicted by calculations in the case of ${}^{209}{Bi}$ .

Energy Division in $π^{-}$ -Nucleus Collisions at 1.5 GeV

J. E. Butt and D. T. King

Phys. Rev. C 8, 359 (1973) - Published 1 July, 1973

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The angular distributions and secondary spectra have been determined for protons and charged pions emergent from collisions of 1.5-GeV negative pions with emulsion nuclei. Expressed in terms of numbers of particles per collision, these results are compared to the predictions of the Monte Carlo intranuclear cascade, averaged over the light- and heavy-target nuclei. The charged-pion spectrum is found to be in large disagreement with that calculated. With included observations on neutral-pion emission, the fraction of primary energy carried away by pions is (16±4)%, where the calculation predicts 48%. Possible reasons for this discrepancy are discussed, and a long-standing question of apparent energy imbalance in these collisions is revived.

Evidence of a Low-Intensity $β^{-}$ Transition in the Disintegration of ${}^{99}{Tc}$

J. Legrand and J. Morel

Phys. Rev. C 8, 366 (1973) - Published 1 July, 1973

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Search for a Zero-Phonon Gamma-Ray Transition in ${}^{108}{Pd}$ and ${}^{134}{Ba}$

P. H. Stelson, S. Raman, J. A. McNabb, R. W. Lide, and C. R. Bingham

Phys. Rev. C 8, 368 (1973) - Published 1 July, 1973

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The nuclear quadrupole vibrational model allows one-phonon transitions but forbids both two-phonon and zero-phonon transitions. Whereas there exists a large amount of experimental information on the degree of forbiddenness of two-phonon transitions, there is little meaningful information on zero-phonon transitions. We have looked for the zero-phonon transition between the first $4^{+}$ state and the second $2^{+}$ state (between members of the two-phonon triplet) in the vibrational-type nuclei ${}^{108}{Pd}$ and ${}^{134}{Ba}$ . We were not able to detect the zero-phonon $γ$ rays. The limits set on the intensities of these transitions lead to notable degrees of forbiddenness. For ${}^{108}{Pd}$ and ${}^{134}{Ba}$ , respectively the ratio $\frac{{B (E 2)}_{4 \to 2}}{{B (E 2)}_{4 \to 2^{'}}}$ is greater than 80 and 360 (limits based on two standard deviations). For these nuclei the forbiddenness of a zero-phonon transition is at least as large as the forbiddenness of a two-phonon transition.

Inelastic Scattering of ${}^{12}C$ on ${}^{12}C$

R. Wieland, A. Gobbi, L. Chua, M. W. Sachs, D. Shapira, R. Stokstad, and D. A. Bromley

Phys. Rev. C 8, 37 (1973) - Published 1 July, 1973

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The elastic and inelastic scattering channels in the ${}^{12}{C +}$ ${}^{12}C$ interaction have been measured for the angles $θ_{lab} = 15.5 ° - 50.5 °$ over the energy range $E_{lab} = 40 - 60$ MeV in steps of 1° and 500 keV, respectively. The strength of the single and mutual excitation of the first excited state (4.43 MeV, $2^{+}$ ) in ${}^{12}C$ was found to be comparable in magnitude to that of the elastic channel over the entire range of the measurement. The implications for the need of coupled-channel analysis of certain heavy-ion scattering systems are discussed, and comparisons between the predictions of certain coupled-channel reaction models and the data are presented.

Excitation Functions and Recoil Ranges of Residual Nuclei Produced through Kr-Induced Transfer Reactions in ${}^{209}{Bi}$ Targets

R. Bimbot and M. F. Rivet

Phys. Rev. C 8, 375 (1973) - Published 1 July, 1973

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The excitation functions and projected recoil ranges for ${}^{211}{At}$ , ${}^{210}{Rn}$ , and ${}^{211}{Rn}$ produced through ${}^{84}{Kr}$ + ${}^{209}{Bi}$ reactions have been measured from 430 to 500 MeV. Substantial values have been found for the cross sections at high energies. The general features of the reactions (the shapes of the excitation functions and the variation of recoil range versus incident energy) are very similar to results found with lighter projectiles and are unambiguously characteristic of non-compound-nucleus processes. Complementary measurements performed on a natural T1 target show that the cross sections for four-charge- and five-charge-transfer reactions are of the order of 1 mb. Therefore, in the reactions ${}^{84}{Kr}$ + ${}^{209}{Bi}$ → ${}^{211}{At}$ , ${}^{210 - 211}{Rn}$ , the contribution of the four- and five-charge transfers followed by fast $α$ decay is not significant, and the main mechanisms involved are the transfers of two and three charges.

Gamma Cascades in ${}^{252}{Cf}$ Spontaneous Fission Fragments

F. F. Hopkins, John R. White, C. Fred Moore, and Patrick Richard

Phys. Rev. C 8, 380 (1973) - Published 1 July, 1973

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A $γ$ -ray- $γ$ -ray coincidence experiment to measure transitions in the spontaneous fission fragments of ${}^{252}{Cf}$ has been performed with a 0.14- ${cm}^{3}$ Ge(Li) detector (full width at half maximum 600 eV at 81 keV) and a 40- ${cm}^{3}$ Ge(Li) detector (full width at half maximum 2.8 keV at 1.33 MeV) in close geometry and repeated in an extended geometry involving shielding of one of the prompt fragments. Several low-energy cascades have been detected which were previously unreported. In addition partial decay schemes for four of the products, ${}^{105}{Mo}$ , ${}^{109}{Ru}$ , ${}^{111}{Ru}$ , and ${}^{146}{La}$ , have been suggested.

Determination of the Static Quadrupole Moment of the First $2^{+}$ State in ${}^{170}{Er}$ by Coulomb Excitation Using ${}^{81}{Br}$ Projectiles

Wendell R. Lutz, James A. Thomson, Rolf P. Scharenberg, Ronald D. Larsen, and Roderick G. Kerr

Phys. Rev. C 8, 391 (1973) - Published 1 July, 1973

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In order to cross-check the reorientation effect as a method of determining nuclear quadrupole moments, we have measured the quadrupole moment of the first $2^{+}$ state in the "rotational" nucleus ${}^{170}{Er}$ . A ${}^{81}{Br}$ projectile was used to maximize the magnitude of the reorientation effect while reducing higher-state corrections to negligible amounts. We found $Q_{2^{+}} = - 1.94 \pm 0.23$ b for the 79-keV $2^{+}$ state in ${}^{170}{Er}$ , which is in excellent agreement with the rotational value $| Q_{2^{+}} (rot) | = 2.15 \pm 0.04$ b.

Corroboration of the Quadrupole Assignment for the 11-MeV Giant Resonance in ${}^{208}{Pb}$

M. B. Lewis, F. E. Bertrand, and D. J. Horen

Phys. Rev. C 8, 398 (1973) - Published 1 July, 1973

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Inelastic scattering of protons with incident energy of 66 MeV has been used to study details of the giant-resonance region for several targets. Examination with high resolution of the recently observed resonance in ${}^{208}{Pb}$ at $E = 11$ MeV reveals fine structure. The data were compared with theoretical predictions for $L = 2$ and $L = 0$ angular distributions. Only the quadrupole interpretation was found to be consistent with the data.

Comment on $M 2 - E 1$ Mixing Observed in ( $γ, γ^{'}$ ) Reactions

R. Moreh, A. Wolf, and O. Shahal

Phys. Rev. C 8, 401 (1973) - Published 1 July, 1973

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Spatial Localization Effects in the ${}^{2}H (d, p d) n$ Reaction

W. von Witsch, G. S. Mutchler, G. C. Phillips, and D. Miljanić

Phys. Rev. C 8, 403 (1973) - Published 1 July, 1973

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A phenomenological explanation is proposed for the pronounced peaks observed in some coincidence spectra of the ${}^{2}H (d, p d) n$ reaction at low relative energies in the proton-neutron system. It is shown that the density-of-states formalism of Phillips, Griffy, and Biedenharn which includes explicitly the fact that the $p - n$ system is produced in a spatially localized state can describe the observed spectral shapes with the pure, isospin-allowed, ${}^{3}S_{1}$ proton-neutron final-state interaction. In addition, the model satisfactorily describes the case of low relative energy between the deuteron and neutron.

Superstrange Nuclei

A. K. Kerman and M. S. Weiss

Phys. Rev. C 8, 408 (1973) - Published 1 July, 1973

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Nuclear Polarization and the Muonic X-Ray Spectrum of Pb

C. M. Shakin and M. S. Weiss

Phys. Rev. C 8, 411 (1973) - Published 1 July, 1973

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The importance of nuclear core excitation for the muonic x-ray spectrum of lead is emphasized. The consideration of octupole nuclear polarization is shown to affect the position of the $3 d$ levels in muonic ${}^{308}{Pb}$ . Inclusion of the nuclear polarization effects may aid in the explanation of an anomaly found by Ford and Rinker in their analysis of muonic transitions in the lead isotopes, as level shifts due to core polarization are of the order of the discrepancies between theory and experiment.

Decay of the 8-min ${}^{157}{Sm}$

N. Kaffrell

Phys. Rev. C 8, 414 (1973) - Published 1 July, 1973

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After the bombardment of enriched ${}^{160}{Gd}$ with 14-MeV neutrons a new 8.0 ± 0.5-min nuclide has been observed which is assigned to the ( $n, α$ ) product ${}^{157}{Sm}$ . A total of 14 $γ$ rays has been found following the decay of ${}^{157}{Sm}$ with the strongest peaks at 121.0, 196.4, 197.8, 394.2, and 844.0 keV. A decay scheme for ${}^{157}{Sm}$ is proposed.

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Some Nuclear Lifetimes in ${}^{18}O$ , ${}^{18}F$ , and ${}^{20}F$

E. K. Warburton, P. Gorodetzky, and J. A. Becker

Phys. Rev. C 8, 418(R) (1973) - Published 1 July, 1973

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The Doppler-shift attenuation method was used in conjunction with ${}^{16}O$ and ${}^{18}O$ bombardment of tritium targets to measure the mean lives of five levels in ${}^{18}O$ , ${}^{18}F$ , and ${}^{20}F$ . The results are [nucleus, $E_{x}$ (keV), $τ$ (psec)]: [ ${}^{18}O$ , 3632, 1.45 ± 0.25]; [ ${}^{18}F$ , 1701, 1.16 ± 0.12]; [ ${}^{20}F$ , 984, 2.30 ± 0.25]; [ ${}^{20}F$ , 1309, 1.45 ± 0.25]; and [ ${}^{20}F$ , 1971, 1.40 ± 0.40].

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Determination of Fractional-Parentage Coefficients from Inelastic Scattering of Protons through Analog Resonances

B. J. Verhaar and W. P. Th. M. van Eeghem

Phys. Rev. C 8, 420(R) (1973) - Published 1 July, 1973

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Nuclear fractional-parentage coefficients, determined from inelastic proton scattering through isobaric analog resonances, are shown to be subject, in some circumstances, to a particular type of ambiguity. A simple linear transformation connects sets of such coefficients giving rise to indistinguishable resonance contributions to differential cross-section and analyzing power, if the relatively weak $j$ dependence of penetration factors, resonance mixing phases, and real optical-model phase shifts is neglected.

RAPID COMMUNICATION

Half-Lives of ${}^{179}{Hf}^{m_{2}}$ and ${}^{177}{Lu}^{m}$

Y. Y. Chu and T. E. Ward

Phys. Rev. C 8, 422(R) (1973) - Published 1 July, 1973

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The half-lives of ${}^{179}{Hf}^{m_{2}}$ and ${}^{177}{Lu}^{m}$ were determined to be 24.8 ± 0.3 and 160.9 ± 0.3 day, respectively, using chemically and isotopically pure sources. The former is significantly lower than the literature value of 29 ± 1 day and the latter is in excellent agreement with the recent literature value of 161.0 ± 0.3 day.

Mean Lifetimes of Levels in ${}^{26}{Al}$

C. R. Gould, D. R. Tilley, and N. R. Roberson

Phys. Rev. C 8, 423 (1973) - Published 1 July, 1973

Single-Particle Density of the Renormalized Fermi-Gas Model

Sudip Kumar Ghosh and Aparesh Chatterjee

Phys. Rev. C 8, 423 (1973) - Published 1 July, 1973

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Identification of ${}^{184}{Hf}$

Studies of ${}^{205}{Bi}$ and ${}^{207}{Bi}$ by Proton-Transfer Reactions

Energy Division in $π^{-}$ -Nucleus Collisions at 1.5 GeV

Evidence of a Low-Intensity $β^{-}$ Transition in the Disintegration of ${}^{99}{Tc}$

Search for a Zero-Phonon Gamma-Ray Transition in ${}^{108}{Pd}$ and ${}^{134}{Ba}$

Inelastic Scattering of ${}^{12}C$ on ${}^{12}C$

Excitation Functions and Recoil Ranges of Residual Nuclei Produced through Kr-Induced Transfer Reactions in ${}^{209}{Bi}$ Targets

Gamma Cascades in ${}^{252}{Cf}$ Spontaneous Fission Fragments

Determination of the Static Quadrupole Moment of the First $2^{+}$ State in ${}^{170}{Er}$ by Coulomb Excitation Using ${}^{81}{Br}$ Projectiles

Corroboration of the Quadrupole Assignment for the 11-MeV Giant Resonance in ${}^{208}{Pb}$

Comment on $M 2 - E 1$ Mixing Observed in ( $γ, γ^{'}$ ) Reactions

Spatial Localization Effects in the ${}^{2}H (d, p d) n$ Reaction

Superstrange Nuclei

Nuclear Polarization and the Muonic X-Ray Spectrum of Pb

Decay of the 8-min ${}^{157}{Sm}$

Some Nuclear Lifetimes in ${}^{18}O$ , ${}^{18}F$ , and ${}^{20}F$

Determination of Fractional-Parentage Coefficients from Inelastic Scattering of Protons through Analog Resonances

Half-Lives of ${}^{179}{Hf}^{m_{2}}$ and ${}^{177}{Lu}^{m}$

Mean Lifetimes of Levels in ${}^{26}{Al}$

Single-Particle Density of the Renormalized Fermi-Gas Model

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