Recent Articles

$K$ -shell internal-ionization probabilities in nuclear $β^{-}$ decay

H. H. Hansen and K. Parthasaradhi

Phys. Rev. C 9, 1143 (1974) - Published 1 March, 1974

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Total $K$ -shell internal-ionization probabilities have been determined by x-ray spectroscopy with a high-energy-resolution Si(Li) detector for the $β^{-}$ -decaying isotopes ${}^{45}{Ca}$ , ${}^{89}{Sr}$ , ${}^{90}{Sr}$ , ${}^{90}Y$ , ${}^{99}{Tc}$ , ${}^{147}{Pm}$ , and ${}^{185}W$ . The number of emitted $K$ x rays were measured in comparison to the absolute $β^{-}$ -decay rate. The results are compared with earlier experimental values and recent theoretical calculations of Law and Campbell. Good agreement is found between theory and experiment.

[RADIOACTIVITY $β^{-}$ emitters ${}^{45}{Ca}$ , ${}^{89}{Sr}$ , ${}^{90}{Sr}$ , ${}^{90}Y$ , ${}^{99}{Tc}$ , ${}^{147}{Pm}$ , and ${}^{185}W$ ; measured $K$ -shell internal-ionization probabilities. Si(Li) x-ray detector, 260 eV at 5.9 keV.]

Background ( $γ, n$ ) cross section in ${}^{208}{Pb}$

H. E. Jackson

Phys. Rev. C 9, 1148 (1974) - Published 1 March, 1974

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A series of experimental estimates of the nonresonant radiative neutron reaction cross section in ${}^{208}{Pb}$ have been reported recently. To date, the results from ( $γ, n$ ) studies have been inconsistent with measurements of neutron-induced reactions. In an effort to resolve this discrepancy, the shape of the 41-keV resonance in the reaction ${}^{208}{Pb} (γ, n) {}^{207}{Pb}$ has been studied in detail by simultaneous measurements of the photoneutron spectra at 90 and 135°. A small asymmetry in the resonance shape implies the presence of a background cross section of ${1.3}_{- 0.7}^{+ 2.7}$ mb. This value can be explained in terms of contributions from neighboring resonances plus a small direct-reaction component; there is no evidence for anomalous processes. The result is consistent with the most recent data from study of the reaction ${}^{207}{Pb} (n, γ_{0})$ .

[NUCLEAR REACTIONS ${}^{208}{Pb} (γ, n)$ , bremsstrahlung end points 7.9, 8.4, and 9.0 MeV; studied shape 41-keV resonance, deduced background $σ (γ, n) = {1.3}_{- 0.7}^{+ 2.7}$ mb.]

Delbrück and nuclear Raman scattering of 10.83-MeV photons by deformed and spherical heavy nuclei

H. E. Jackson, G. E. Thomas, and K. J. Wetzel

Phys. Rev. C 9, 1153 (1974) - Published 1 March, 1974

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A beam of monoenergetic $γ$ rays, extracted from the CP-5 reactor, has been used in a high-resolution measurement of the differential cross sections for photon scattering by Tb, Ta, Pb, Bi, Th, and ${}^{238}U$ . The spectrum of scattered photons was observed with a resolution of ∼ 10 keV in a Ge(Li) detector whose sensitive volume was ∼ 60 ${cm}^{3}$ . For Pb and U extensive measurements of the angular distributions for elastic and inelastic scattering were measured. For scattering angles $θ < 45^{\circ}$ the elastic scattering is dominated by the Delbrück effect. With the possible exception of Ta, for $θ > 90^{\circ}$ (where only nuclear resonance and Thomson scattering are important) both the magnitude and angular dependence of the elastic scattering cross section are in good agreement with the values which follow from the most recent photoabsorption cross sections in the corresponding targets. To an accuracy of ∼ 10% the elastic and inelastic (nuclear Raman) scattering for U and Th can be deduced from the simple rotator model using the parameters implied by the photoabsorption data. A trend of Raman scattering to be 10% weaker than expected is suggested by the data. For Ta and Tb the Raman scattering is substantially weaker than expected.

[NUCLEAR REACTIONS ${}^{159}{Tb}$ , ${}^{181}{Ta}$ , Pb, ${}^{209}{Bi}$ , ${}^{232}{Th}$ , ${}^{238}U (γ, γ^{'})$ , $E_{γ} = 10.83$ MeV; measured $σ (θ)$ , elastic scattering, inelastic scattering to g.s. rotational band. Ge(Li) detector, 10 keV at 10 MeV.]

Alpha decay of ${}^{215}{Fr}$

T. Nomura, K. Hiruta, M. Yoshie, and O. Hashimoto

Phys. Rev. C 9, 1168 (1974) - Published 1 March, 1974

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The $α$ -decay property of ${}^{215}{Fr}$ has been studied by the pulsed-beam method, in which ${}^{215}{Fr}$ was produced in the ${}^{209}{Bi} ({}^{12}C, α 2 n)$ reaction and its $α$ decay was measured between natural beam bursts of the cyclotron. The ground state of ${}^{215}{Fr}$ was found to decay with $E_{α} = 9.355 \pm 0.010$ MeV and $t_{\frac{1}{2}} = 0.12 \pm 0.02$ μsec. The reduced $α$ width of ${}^{215}{Fr}$ is shown to fit the systematical trend of $N = 128$ isotones very well and to agree with the simple shell-model calculation. Distributions of recoil angles for reaction products in the ( ${}^{12}C, α xn$ ) reaction were found to be quite different from those for ( ${}^{12}C, x n$ ) products, giving a convenient method of distinguishing these reaction products.

[NUCLEAR REACTIONS ${}^{209}{Bi} ({}^{12}C, x n)$ , ${}^{209}{Bi} ({}^{12}C, α x n)$ , $E = 73 - 80$ MeV; measured $α$ decay and $W (θ)$ of reaction products, $E_{α}$ , $t_{\frac{1}{2}}$ ; deduced $α$ -decay width of ${}^{215}{Fr}$ .]

Electric monopole strength in ${}^{100}{Ru}$

Masahiro Koike, Hirokane Kawakami, and Ko Sakamoto

Phys. Rev. C 9, 1174 (1974) - Published 1 March, 1974

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The electric monopole transition from the 1130-keV ( $0^{+}$ ) state of ${}^{100}{Ru}$ has been found from internal-conversion-electron studies of the decay of ${}^{100}{Pd}$ . The observed branching ratio of the conversion-electron emission of the crossover $E 0$ and cascade $E 2$ transitions $\frac{J_{eK} (E 0)}{J_{eK} (E 2)}$ is 0.075. The electric monopole strength $ρ (E 0)$ has an upper limit of 0.089.

[RADIOACTIVITY ${}^{100}{Pd}$ [from ${}^{103}{Rh} (p, 4 n)$ ]; measured $E_{ce}$ , $I_{ce}$ , $E_{γ}$ , $I_{γ}$ . ${}^{100}{Ru}$ deduced branching ratio $\frac{E 0}{E 2}$ , ICC.]

Investigation of the $γ$ decay of subthreshold-fission resonances of ${}^{242}{Pu}$ to a fission isomeric state

J. C. Browne and C. D. Bowman

Phys. Rev. C 9, 1177 (1974) - Published 1 March, 1974

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A pure class-II state can be defined in terms of a double-humped fission barrier as a state in the second well which has two modes of decay: fission through the outer barrier ( $Γ_{f II}$ ) and $γ$ decay ( $Γ_{γ II}$ ) to the ground state in the second well (fission isomer). The purpose of this experiment was to measure the branching ratio ( $\frac{Γ_{γ II}}{Γ_{f II}}$ ) for an almost-pure class-II state in the ${}^{242}{Pu} + n$ system, thereby establishing for the first time a direct connection between fission intermediate structure and shape isomerism. A 10-g sample of ${}^{242}{Pu}$ was bombarded by neutrons from the Livermore 100-MeV linac. Both the energy of a neutron inducing an event and the time relationship between $γ$ rays detected in a pair of $C_{6}$ $D_{6}$ scintillators were stored in a two-dimensional matrix consisting of 7.7× $10^{5}$ channels. Analysis of subthreshold fission groups at neutron energies of 763 and 1839 eV showed no evidence of a $γ$ -decay branch to the 33-nsec fission isomer in ${}^{243}{Pu}$ . From the limit on the branching ratio ( $\frac{Γ_{γ II}}{Γ_{f II}}$ ) obtained from these data, an upper limit of $Γ_{γ II} < 1$ meV was derived. Since theoretical calculations predict $Γ_{γ II} \approx 8 - 10$ meV for ${}^{243}{Pu}$ , the experiment had a sensitivity which is a factor of 10 lower than should have been necessary to observe the $γ$ decay to the fission isomer. From the present results and from previous measurements on ${}^{243}{Pu}$ , we are led to the conclusion that there may exist an additional longer-lived isomer in ${}^{243}{Pu}$ similar to the other odd-Pu isotopes.

[NUCLEAR REACTIONS ${}^{242}{Pu} + n$ , $E = 400 - 3000$ eV; investigated $γ$ decay to fission isomer in ${}^{243}{Pu}$ ; deduced limit on $\frac{Γ_{γ II}}{Γ_{f II}}$ ; predicted an additional isomer in ${}^{243}{Pu}$ .]

Sum rules and the nonexchange force

Toshio Suzuki and Chikara Hinohara

Phys. Rev. C 9, 1186 (1974) - Published 1 March, 1974

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Remark on the transition-operator boson

Susumu Okubo

Phys. Rev. C 9, 1188 (1974) - Published 1 March, 1974

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The transition-operator boson introduced by Dreizler and Klein has been analyzed in detail, and the exact expression for angular momentum operators in terms of the boson has been obtained. The method is found to be applicable only in the asymptotic limit of the large nuclear number. Its relation to another representation due to Holstein and Primakoff has also been investigated.

Status of nuclear coexistence for ${}^{32}S$

Y. T. Cheng, A. Goswami, M. J. Throop, and D. K. McDaniels

Phys. Rev. C 9, 1192 (1974) - Published 1 March, 1974

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The mean lifetime of the $0^{+}$ state at 3.778 MeV in ${}^{32}S$ has been carefully remeasured by the Doppler-shift-attenuation method, using the reaction ${}^{31}P (p, γ) {}^{32}S$ . This lifetime has been combined with other information to obtain a good experimental value for the admixture of the deformed and spherical states in ${}^{32}S$ , thereby confirming the validity of the coexistence picture for this nucleus.

[NUCLEAR REACTIONS ${}^{31}P (p, γ)$ , $E = 0.811, 1.117, and 1.583$ MeV; ${}^{32}S$ , measured $τ$ , DSAM.]

Comments on $E 1 : M 2$ competition in ${}^{154}{Gd}$

K. E. G. Löbner and M. E. Bunker

Phys. Rev. C 9, 1196 (1974) - Published 1 March, 1974

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Nuclear-Coulomb interference in $π^{+} - {}^{12}C$ scattering

G. S. Mutchler, M. L. Scott, C. R. Fletcher, E. V. Hungerford, L. V. Coulson, N. D. Gabitzsch, G. C. Phillips, B. W. Mayes, L. Y. Lee, J. C. Allred, and Clark Goodman

Phys. Rev. C 9, 1198 (1974) - Published 1 March, 1974

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The small angle scattering of $π^{+}$ from ${}^{12}C$ was measured at 115, 167, and 242 MeV from 3 to 10°. These measurements covered the Coulomb-nuclear interference region. New values of the $π^{+} - {}^{12}C$ total cross section have been used to extract the real part of the forward-scattering amplitude.

[NUCLEAR REACTION ${}^{12}C (π^{+}, π^{+})$ , $E = 115 - 242$ MeV; measured $σ (θ_{π})$ ; deduced $\frac{Re f_{N} (0^{\circ})}{Im f_{N} (0^{\circ})}$ .]

Lifetimes of levels in ${}^{24}{Ne}$

B. A. Watson, J. A. Becker, and T. R. Fisher

Phys. Rev. C 9, 1200 (1974) - Published 1 March, 1974

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Nuclear lifetimes of levels in ${}^{24}{Ne}$ have been measured by employing the ${}^{22}{Ne} (t, p)$ reaction at a triton bombarding energy of 2.9 MeV. Protons were detected by an annular silicon surface-barrier detector at an average angle of 174°, and coincident $γ$ rays were detected by a Ge(Li) detector positioned at angles of 30 and 120°. Nuclear lifetimes were extracted by the Doppler-shift-attenuation technique. Measured lifetimes of the 1.98, 3.87, and 4.76 levels are ${0.89}_{- 0.29}^{+ 0.36}$ , < 0.18, and ${3.3}_{- 1.2}^{+ 2.1}$ psec. The experimental results are well reproduced by the shell-model calculations of Robertson and Wildenthal.

[NUCLEAR REACTIONS ${}^{22}{Ne} (t, p)$ , $E_{t} = 2.8$ MeV; measured $σ (E_{p}, E_{γ}, θ_{γ})$ . ${}^{24}{Ne}$ deduced $τ_{m}$ . Solid Ne target; Doppler shift attenuation.]

Level-level correlations in Hauser-Feshbach theory and Moldauer's sum rule for resonance reactions

Hans A. Weidenmüller

Phys. Rev. C 9, 1202 (1974) - Published 1 March, 1974

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It is shown that Moldauer's sum rule is equivalent to analyticity and unitarity of the $S$ matrix. Inconsistencies derived from the sum rule with the help of some approximation thus indicate that the approximation violates unitarity. It is also shown that a derivation of the Hauser-Feshbach formula beyond the regime of small absorption in all channels is possible only in the frame of a dynamical model for the compound nucleus.

Angle transformation for the $π$ -nucleus optical potential

E. Kujawski and G. A. Miller

Phys. Rev. C 9, 1205 (1974) - Published 1 March, 1974

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The transformation of the $π$ -nucleon $T$ matrix from the $π$ -nucleon to the $π$ -nucleus center-of-mass systems is investigated. The correct angle transformation is presented, and it is shown to yield straightforward corrections to the usual Kisslinger and local Laplacian potentials consisting of terms proportional to $\nabla^{2} ρ$ and $\nabla^{4} ρ$ where $ρ$ is the target density. Numerical results are presented for $π^{-} - {}^{12}C$ elastic scattering at 120- and 180-MeV lab kinetic energy.

[NUCLEAR REACTIONS $π^{-} - {}^{12}C$ elastic scattering at 120 and 180 MeV, theoretical optical potential.]

${}^{6}{Li}$ cluster-model phenomenology

J. V. Noble

Phys. Rev. C 9, 1209 (1974) - Published 1 March, 1974

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A phenomenological $α + d$ cluster-model wave function for the ${}^{6}{Li}$ ground state is suggested and its properties fixed using data on the static $M 1$ and $E 2$ moments and elastic charge form factors of ${}^{6}{Li}$ . The resulting $α + d$ momentum distribution is then compared with that deduced from knockout and transfer reactions.

[NUCLEAR STRUCTURE ${}^{6}{Li}$ , phenom. $α + d$ cluster-model wave function; parameters determined from elastic charge form factor and static $M 1$ and $E 2$ moments. Calculated $α + d$ momentum distribution compared reactions. ${}^{6}{Li} (α, 2 α)$ , ${}^{6}{Li} (π^{-}, 2 n)$ , ${}^{12}C ({}^{6}{Li}, d)$ .]

Half-lives of ${}^{10}C$ , ${}^{14}O$ , and ${}^{23}{Mg}$

G. Azuelos, J. E. Crawford, and J. E. Kitching

Phys. Rev. C 9, 1213 (1974) - Published 1 March, 1974

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Evidence for the nonperipheral capture of heavy negative particles by tantalum

W. M. Bugg, G. T. Condo, E. L. Hart, and H. O. Cohn

Phys. Rev. C 9, 1215 (1974) - Published 1 March, 1974

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A comparison of the data from our previous experiments utilizing stopping $\tilde{p}$ and $K^{-}$ mesons in solid materials suggests that the nuclear capture of these particles may not be confined to the nuclear periphery in the case of tantalum. Other evidence supportive of this hypothesis is also presented.

[NUCLEAR STRUCTURE ${}^{181}{Ta}$ ; $\tilde{p}$ and $K^{-}$ capture at rest; surface density of neutrons.]

${}^{3}{He} ({}^{3}{He}, 2 p) {}^{4}{He}$ and the termination of the proton-proton chain

M. R. Dwarakanath

Phys. Rev. C 9, 805 (1974) - Published 1 March, 1974

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Following a suggestion by Fowler, Fetisov, and Kopysov, we have extended our earlier measurements of total cross section for ${}^{3}{He} ({}^{3}{He}, 2 p) {}^{4}{He}$ to energies as low as $E_{c . m .} = 30$ KeV. The measured cross-section factors are in good agreement with the currently accepted empirical relation $S (E_{c . m .}) = (5.2 - 2.8 E_{c . m .} + 1.4 E_{c . m .}^{2})$ MeVb. We have also searched the energy interval $14 keV < E_{c . m .} < 28 keV$ for a narrow resonance in ${}^{3}{He} ({}^{3}{He}, 2 p) {}^{4}{He}$ and the results of these measurements form the subject of this paper.

[NUCLEAR REACTIONS ${}^{3}{He} ({}^{3}{He}, 2 p) {}^{4}{He}$ , $E_{c . m .} = 30 - 150$ keV; measured $σ (E)$ ; also searched for a narrow resonance. Gas target.]

Effect of short-range correlations on Coulomb matrix elements

R. J. McCarthy and G. E. Walker

Phys. Rev. C 9, 809 (1974) - Published 1 March, 1974

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Correlated wave functions obtained by solving the Bethe-Goldstone equation with the Hamada-Johnston potential are used to calculate Coulomb matrix elements for use in the nuclear $1 p$ shell. When proper attention is given to the Pauli operator we find that Coulomb matrix elements are not appreciably larger than those obtained using uncorrelated wave functions, in contrast to conclusions reached by previous investigators.

Effect of short-range correlations on Coulomb matrix elements

Paul Goldhammer

Phys. Rev. C 9, 813 (1974) - Published 1 March, 1974

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Recent Articles

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Recent Issues

$K$ -shell internal-ionization probabilities in nuclear $β^{-}$ decay

Background ( $γ, n$ ) cross section in ${}^{208}{Pb}$

Delbrück and nuclear Raman scattering of 10.83-MeV photons by deformed and spherical heavy nuclei

Alpha decay of ${}^{215}{Fr}$

Electric monopole strength in ${}^{100}{Ru}$

Investigation of the $γ$ decay of subthreshold-fission resonances of ${}^{242}{Pu}$ to a fission isomeric state

Sum rules and the nonexchange force

Remark on the transition-operator boson

Status of nuclear coexistence for ${}^{32}S$

Comments on $E 1 : M 2$ competition in ${}^{154}{Gd}$

Nuclear-Coulomb interference in $π^{+} - {}^{12}C$ scattering

Lifetimes of levels in ${}^{24}{Ne}$

Level-level correlations in Hauser-Feshbach theory and Moldauer's sum rule for resonance reactions

Angle transformation for the $π$ -nucleus optical potential

${}^{6}{Li}$ cluster-model phenomenology

Half-lives of ${}^{10}C$ , ${}^{14}O$ , and ${}^{23}{Mg}$

Evidence for the nonperipheral capture of heavy negative particles by tantalum

${}^{3}{He} ({}^{3}{He}, 2 p) {}^{4}{He}$ and the termination of the proton-proton chain

Effect of short-range correlations on Coulomb matrix elements

Effect of short-range correlations on Coulomb matrix elements

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