Recent Articles

RAPID COMMUNICATION

Decay rates for doubly even $N = 84$ $α$ emitters and the subshell closure at $Z = 64$

W. -D. Schmidt-Ott and K. S. Toth

Phys. Rev. C 13, 2574(R) (1976) - Published 1 June, 1976

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Up-to-date decay energies and half-lives for doubly even $N = 84$ $α$ emitters (from ${}^{144}{Nd}$ to ${}^{154}{Yb}$ ) were used to determine their reduced widths for $α$ decay. It was found that, as had been predicted earlier by Bardeen-Cooper-Schrieffer calculations, the reduced widths reach a minimum at $Z = 64$ and not at $Z = 66$ , as older data had indicated. As part of the study the $α$ -decay energy of ${}^{154}{Yb}$ was redetermined to be 5.318±0.005 MeV.

RADIOACTIVITY ${}^{154}{Yb}$ ; redetermined $E_{α}$ . ${}^{144}{Nd}$ , ${}^{146}{Sm}$ , ${}^{148}{Gd}$ , ${}^{150}{Dy}$ , ${}^{152}{Er}$ , ${}^{154}{Yb}$ ; deduced $α$ -decay reduced width.

RAPID COMMUNICATION

Evidence for a triple-hump shaped fission barrier in light actinides

A. Gavron, H. C. Britt, and J. B. Wilhelmy

Phys. Rev. C 13, 2577(R) (1976) - Published 1 June, 1976

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RAPID COMMUNICATION

Multistep processes in the ${}^{19}F$ ( ${}^{16}O$ , ${}^{15}N$ ) ${}^{20}{Ne}$ reaction

K. S. Low, T. Tamura, and T. Udagawa

Phys. Rev. C 13, 2579(R) (1976) - Published 1 June, 1976

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An exact-finite-range coupled-channels Born-approximation analysis, which takes into account multistep processes, was made of the reaction ${}^{19}F$ ( ${}^{16}O$ , ${}^{15}N$ ) ${}^{20}{Ne}$ ( $0^{+}$ , $2^{+}$ , $4^{+}$ ). Good fits to data were obtained not only for the $0^{+}$ and $2^{+}$ state cross sections, but also for the $4^{+}$ state which is forbidden in a one-step process. Deviation of the distorted-wave Born-approximation result from the coupled-channel Born-approximation result was observed even for the allowed transition to the $0^{+}$ and $2^{+}$ states.

NUCLEAR REACTIONS ${}^{19}F$ ( ${}^{16}O$ , ${}^{15}N$ ), $E = 68$ MeV calculated $σ (θ)$ with CCBA and DWBA.

RAPID COMMUNICATION

Inverse scattering and the accuracy of unitary pole approximation

M. L. Sharma, A. P. S. Sirohi, and Lal Singh

Phys. Rev. C 13, 2582(R) (1976) - Published 1 June, 1976

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An attempt has been made to investigate the accuracy of the unitary pole approximation to the K matrix for a rank-two separable nonlocal potential generated in the inverse scattering formalism following Fiedeldey's approach. The repulsive form factor has been determined with the help of the attractive one recently proposed by Sirohi et al. The calculations presented in the manuscript show that the unitary pole approximation is quite a good approximation to the potential and hence can be suitably used in three-body calculations.

NUCLEAR REACTIONS Separable nonlocal $N - N$ interaction in inverse scattering formalism; calculated UPA $K$ -matrix elements; compared with the exact values; studied accuracy of UPA.

RAPID COMMUNICATION

Doorway effects in the ${}^{206}{Pb} (n, γ) {}^{207}{Pb}$ cross section

Amos Lev and William P. Beres

Phys. Rev. C 13, 2585(R) (1976) - Published 1 June, 1976

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A projection operator formalism that includes doorway effects is used to calculate the ${}^{206}{Pb} (n, γ) {}^{207}{Pb}$ cross section near 0.5 MeV where conflicting experimental results have been reported. We do not resolve these conflicts in this work. However, we do predict a doorway at this energy. We find that calculations including the effects of this doorway in modifying the valency capture rate yield ( $n, γ$ ) cross sections are considerably smaller than that observed by Baglan et al., and therefore appear to rule out the valence-doorway interpretation advanced by those authors.

NUCLEAR REACTIONS ${}^{206}{pb} (n, γ) {}^{207}{Pb}$ , $σ (n, γ)$ calculated for $s$ waves, $E = 0 - 2$ MeV, particle-vibration doorways.

RAPID COMMUNICATION

Absolute cross sections for the ${}^{61}{Ni} ({}^{16}O, 3 n) {}^{74}{Kr}$ reaction

J. C. Wells, Jr., R. L. Robinson, H. J. Kim, and J. L. C. Ford, Jr.

Phys. Rev. C 13, 2588(R) (1976) - Published 1 June, 1976

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Previously determined absolute cross sections for the ${}^{61}{Ni} ({}^{16}O, 3 n) {}^{74}{Kr}$ reactions are found to be incorrect due to errors in the published level structure of ${}^{74}{Kr}$ . New information on the $β$ -decay of ${}^{74}{Kr}$ has permitted upper limits on the ${}^{61}{Ni} ({}^{16}O, 3 n) {}^{74}{Kr}$ cross sections to be established. These are in agreement with cross sections calculated for statistical evaporation of particles from a compound nucleus.

NUCLEAR REACTIONS ${}^{61}{Ni} ({}^{16}O, 3 n) {}^{74}{Kr}$ , $E_{16_{O}} = 38.5 - 51.0$ MeV; measured $E_{γ}$ , $I_{γ}$ ; deduced $σ (E)$ .

RAPID COMMUNICATION

Magnetic moment of the first excited state of ${}^{121}{Sb}$ and the hyperfine field in ${Pd}_{2}$ MnSb

G. Langouche, N. S. Dixon, Y. Mahmud, B. B. Triplett, S. S. Hanna, and P. Boolchand

Phys. Rev. C 13, 2589(R) (1976) - Published 1 June, 1976

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The Mössbauer effect of ${}^{121}{Sb}$ in ${Pd}_{2}$ MnSb is used to derive a more accurate value for the magnetic moment of the first excited state (37.15 keV): $μ_{e} = (2.518 \pm 0.007) μ_{N}$ . The hyperfine field is found to be 651 ± 5 kOe at 80 K and 706 ± 5 kOe at 18 K.

RADIOACTIVITY ${}^{121}{Sn}^{m}$ in BaSn $O_{3}$ ; measured Mössbauer effect in ${}^{121}{Sb}$ level, $E = 37.15$ keV in ${Pd}_{2}$ MnSb; deduced hyperfine field, ${}^{121}{Sb}$ level deduced $μ$ .

RAPID COMMUNICATION

Low-intensity transition in the decay of ${}^{175}{Hf}$

William W. Pratt

Phys. Rev. C 13, 2591(R) (1976) - Published 1 June, 1976

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A study of the decay of ${}^{175}{Hf}$ has confirmed the presence of a weak transition in ${}^{175}{Lu}$ . A $γ$ ray was found with an energy of 353.3 ± 0.2 keV and an intensity (relative to 100 for the 343 keV $γ$ ray) of 0.21 ± 0.02.

RADIOACTIVITY ${}^{175}{Hf}$ [from ${}^{174}{Hf} (n γ)$ ]; measured $E_{γ}$ , $I_{γ}$ . Natural target, Ge(Li) detector.

RAPID COMMUNICATION

Beta-ray branching in the decay of ${}^{19}{Ne}$

David E. Alburger

Phys. Rev. C 13, 2593(R) (1976) - Published 1 June, 1976

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The $β$ decay of ${}^{19}{Ne}$ has been studied by measuring the $γ$ -ray spectrum with a Ge(Li) detector. Sources were made in the ${}^{19}F (p, n) {}^{19}{Ne}$ reaction by 7.0-MeV proton bombardment of Ca $F_{2}$ or Ba $F_{2}$ targets mounted in a graphite "rabbit." From the intensity of a weak 1357-keV peak relative to 511-keV $γ$ rays the $β^{+}$ branching of ${}^{19}{Ne}$ to the 1554-keV state of ${}^{19}O$ was found to be (2.1 ± 0.3) × $10^{- 5}$ per decay. This is a factor of 2.6 larger than a recently reported value but does not substantially improve the prospects for an experiment designed to study neutral currents in weak interactions.

RADIOACTIVITY ${}^{19}{Ne}$ : measured $I_{γ}$ ; deduced $β^{+}$ branch, $log ft$ value.

Erratum: Levels in the three-hole nucleus ${}^{105}{Ag}$ and the decay of 55.5-min ${}^{105}{Cd}$

S. V. Jackson, W. B. Walters, and R. A. Meyer

Phys. Rev. C 13, 2596 (1976) - Published 1 June, 1976

Erratum: Mean lives and other properties of some levels in Ti

V. K. Rasmussen

Phys. Rev. C 13, 2596 (1976) - Published 1 June, 1976

Erratum: Resonating-group study of $N + {}^{16}O$ scattering with a generator-coordinate technique

D. R. Thompson and Y. C. Tang

Phys. Rev. C 13, 2597 (1976) - Published 1 June, 1976

Measurement of the excitation energy of the 7.654 MeV state of ${}^{12}C$ and the rate of the $3 α$ reaction

J. A. Nolen, Jr. and Sam M. Austin

Phys. Rev. C 13, 1773 (1976) - Published 1 May, 1976

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The excitation energy of the second excited state of ${}^{12}C$ has been measured to be 7654.00 ± 0.20 keV. Combining this result with the recent precise measurement of the atomic mass of ${}^{4}{He}$ by Smith and Wapstra, the $Q$ value for the reaction $3 α \to {}^{12}C (7654.00)$ is determined to be 379.31 ± 0.21 keV. This result implies a change of +9%, at a stellar temperature of $10^{8}$ K, in the $3 α$ reaction rate quoted in the recent compilation of Fowler, Caughlan, and Zimmerman.

NUCLEAR REACTIONS ${}^{12}C$ , ${}^{15}N$ , ${}^{16}O (p, p^{'})$ , $E = 34.75$ MeV; magnetic spectrograph; measured excitation energies of ${}^{12}C$ (7.65 MeV), ${}^{15}N$ (7.56 MeV), and ${}^{16}O$ (6.13 MeV) states with 200 eV uncertainties. Measurement related to astrophysical helium burning ( $3 α$ ) rate.

"Moon crescent effect" in transfer form factors

B. Giraud, J. LeTourneux, and D. Zaikin

Phys. Rev. C 13, 1780 (1976) - Published 1 May, 1976

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It is shown that, when a nucleus is subdivided into a core and a cloud for the calculation of transfer form factors, one should allow for the possible displacement of the core with respect to the center of mass of the entire nucleus. This leads to corrections, which are estimated for a soluble model.

NUCLEAR REACTIONS Generator coordinates prove core is not center of composite nucleus for calculation of DWBA form factor.

Lowest $T = 2$ state of ${}^{36}{Ar}$ via the ${}^{35}{Cl} (p, γ) {}^{36}{Ar}$ reaction

A. Huck, G. J. Costa, G. Walter, M. M. Aleonard, J. Dalmas, P. Hubert, F. Leccia, P. Mennrath, J. Vernotte, M. Langevin, and J. M. Maison

Phys. Rev. C 13, 1786 (1976) - Published 1 May, 1976

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The ${}^{35}{Cl} (p, γ) {}^{36}{Ar}$ reaction was studied in the proton energy range $E_{p} = 2.36 - 2.42$ MeV. Yield curves were obtained using NaI(Tl) and Ge(Li) detectors. The $E_{x} = 10854.2 \pm 1.6$ keV level, populated at the $E_{p} = 2414.4 \pm 1.5$ keV resonance, decays to the $E_{x} = 7711 and 8133$ keV levels with branching ratios of (35 ± 15)% and (65 ± 15)%, respectively. From resonance strength and angular distribution measurements as well as from the comparison with the $γ$ -decay scheme of the lowest $T = 2$ state of ${}^{36}{Cl}$ , the $E_{x} = 10854$ keV level can be assigned definitely $(J^{π}, T) = (0^{+}, 2)$ .

NUCLEAR REACTIONS ${}^{35}{Cl} (p, γ)$ , investigation for the first $T = 2$ level of ${}^{36}{Ar}$ , $E_{p} = 2.36 - 2.42$ MeV measured proton resonance energies, $γ$ -ray branching ratios, resonance strength, $γ$ -ray angular distributions, deduced transition strengths. Enriched targets, Ge(Li) and NaI(Tl) detectors.

Angular correlation and gamma ray linear polarization measurements in ${}^{29}{Al}$

F. A. Beck, T. Byrski, A. Knipper, and J. P. Vivien

Phys. Rev. C 13, 1792 (1976) - Published 1 May, 1976

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The decay scheme of ${}^{29}{Al}$ has been investigated with the ${}^{26}{Mg} (α, p) {}^{29}{Al}$ reaction at $E_{α} = 14.2$ MeV. Simultaneous measurements of $p - γ$ angular correlations and $p - γ$ linear polarizations, utilizing a three-detector Ge(Li) Compton polarimeter, have been accomplished. Spin-parity assignments of ${7 / 2}^{+}$ , ${3 / 2}^{+}$ , ${5 / 2}^{+}$ , ${9 / 2}^{+}$ , ${5 / 2}^{+}$ , and ${7 / 2}^{+}$ are set forth, respectively, for the 1.75, 2.22, 3.18, 3.58, 4.22, and 5.99 MeV levels. The results suggest $J^{π} = {\frac{11}{2}}^{+}$ for the 5.85 MeV level.

NUCLEAR REACTIONS ${}^{26}{Mg} (α, p)$ , $E = 14.2$ MeV; measured $p γ$ coincidence, $E_{γ}$ , $I_{γ} (θ_{γ})$ , $γ$ linear polarizations. ${}^{29}{Al}$ deduced levels, $E_{x}$ , $J$ , $π$ , $δ$ , branching ratios. Enriched target. Ge(Li) Compton polarimeter.

Four-body equations

Tatuya Sasakawa

Phys. Rev. C 13, 1801 (1976) - Published 1 May, 1976

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It is shown that the Yakubovski four-body equation is essentially equal to the equation by some authors, which consists of six coupled equations. A new set of seven coupled four-body equations is derived. By this set of equations, one can treat four-body problems involving any number of bound substructures.

NUCLEAR REACTIONS Scattering theory. Four-body systems. Equivalence of some equations. New coupled equations.

Numerical investigation of minimal three-body equations. II. Resonant pair interactions

R. Aaron, R. D. Amado, and Tohru Takahashi

Phys. Rev. C 13, 1810 (1976) - Published 1 May, 1976

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We apply the "minimal" three-body equations to a simple three-boson model with resonant pair interaction. We show that the isobar or sequential decay amplitude has important variation over the three-body phase space even for relatively weak coupling and we give an approximate analytic expression for that amplitude that reproduces the variation for a wide range of parameters.

NUCLEAR REACTIONS Numerical and analytic investigation of unitarity and analyticity constraints in a resonant three-boson model.

Phase-shift analysis of the 20-30-MeV $pp$ and $np$ scattering data, including new high-precision $np P (θ)$ measurements

G. E. Bohannon, Thomas Burt, and Peter Signell

Phys. Rev. C 13, 1816 (1976) - Published 1 May, 1976

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The available $pp$ and $np$ scattering data in the energy range 20-30 MeV are analyzed and reduced in order to obtain a minimum set without loss of statistically significant information. The new Jones-Brooks and Morris-O'Malley-May-Thornton high-precision $np p (θ)$ data are included. The resulting set of 43 $pp$ and 65 $np$ independent data are augmented by Coulomb splittings of the $pp$ and $np$ isospin-one phase shifts and by high and intermediate angular momentum phase shifts computed from $π n$ , $π π$ , and $en$ data via analyticity and unitarity. Each of these three additions has a significant effect on the low angular momentum phase shifts. The resulting $D$ -wave phase parameters are in much better agreement with the values produced by potential models than were those produced by the earlier Livermore continuous-energy analysis.

NUCLEAR REACTIONS Phase parameter analysis, 20-30-MeV $p p + n p$ data, theoretical input; low- $L$ phases, other analyses, model values.

$K$ operators and unitary approximations for the three-body problem

D. J. Kouri, F. S. Levin, and W. Sandhas

Phys. Rev. C 13, 1825 (1976) - Published 1 May, 1976

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The method of channel coupling arrays is used as a means to introduce unitary approximations for the three-body problem. First, the transition operators defined by the channel coupling array equations are shown to obey the correct (on-shell) discontinuity equations. Next, $K$ (reaction) operators are defined by using principal value Green's functions in the channel coupling array equations. These operators are then shown to be related to the transition operators by a damping equation which leads to the correct discontinuity relation. This development provides the basis for introducing unitary approximations, since any set of $K$ operators having zero discontinuity will yield, through the damping equation, a set of transition operators having the proper singularity structure. The use of the channel coupling array method achieves this result without the need for introducing an intermediate hierarchy of operators, as in other approaches.

NUCLEAR REACTIONS Channel coupling array theory, $K$ operators, unitary approximations, three-body problem.

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Recent Issues

Decay rates for doubly even $N = 84$ $α$ emitters and the subshell closure at $Z = 64$

Evidence for a triple-hump shaped fission barrier in light actinides

Multistep processes in the ${}^{19}F$ ( ${}^{16}O$ , ${}^{15}N$ ) ${}^{20}{Ne}$ reaction

Inverse scattering and the accuracy of unitary pole approximation

Doorway effects in the ${}^{206}{Pb} (n, γ) {}^{207}{Pb}$ cross section

Absolute cross sections for the ${}^{61}{Ni} ({}^{16}O, 3 n) {}^{74}{Kr}$ reaction

Magnetic moment of the first excited state of ${}^{121}{Sb}$ and the hyperfine field in ${Pd}_{2}$ MnSb

Low-intensity transition in the decay of ${}^{175}{Hf}$

Beta-ray branching in the decay of ${}^{19}{Ne}$

Erratum: Levels in the three-hole nucleus ${}^{105}{Ag}$ and the decay of 55.5-min ${}^{105}{Cd}$

Erratum: Mean lives and other properties of some levels in Ti

Erratum: Resonating-group study of $N + {}^{16}O$ scattering with a generator-coordinate technique

Measurement of the excitation energy of the 7.654 MeV state of ${}^{12}C$ and the rate of the $3 α$ reaction

"Moon crescent effect" in transfer form factors

Lowest $T = 2$ state of ${}^{36}{Ar}$ via the ${}^{35}{Cl} (p, γ) {}^{36}{Ar}$ reaction

Angular correlation and gamma ray linear polarization measurements in ${}^{29}{Al}$

Four-body equations

Numerical investigation of minimal three-body equations. II. Resonant pair interactions

Phase-shift analysis of the 20-30-MeV $pp$ and $np$ scattering data, including new high-precision $np P (θ)$ measurements

$K$ operators and unitary approximations for the three-body problem

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