Recent Articles

Elastic scattering of deuterons by ${}^{4}{He}$ between 30 and 40 MeV

H. Willmes, C. R. Messick, T. A. Cahill, D. J. Shadoan, and R. G. Hammond

Phys. Rev. C 10, 1762 (1974) - Published 1 November, 1974

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Differential cross sections for elastic scattering of deuterons by ${}^{4}{He}$ were measured at laboratory energies of 29.8, 32.3, 34.8, 37.3, and 39.8 MeV. The angular range extended from 15 to 160° cm in steps of about 5°. The average relative error was 2%, and the uncertainty in the absolute normalization was 2%.

NUCLEAR REACTIONS ${}^{4}{He} (d, d)$ , $E = 29.8, 32.3, 34.8, 37.3, 39.8$ MeV; measured ( $E, θ_{l}$ ); $θ_{c} = 16 ° to 159 °$ .

Study of the $α + α$ system below 15 MeV (c.m.)

W. S. Chien and Ronald E. Brown

Phys. Rev. C 10, 1767 (1974) - Published 1 November, 1974

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Differential cross sections for $α + α$ elastic scattering have been measured at lab energies of 18.00, 21.12, 24.11, 25.50, 26.99, 28.50, and 29.50 MeV. The majority of the data have relative errors less than 1%, and the additional error in absolute scale is 0.30%. A phase-shift analysis of the data has been performed, and most of the phase shifts have been determined to within $\pm \frac{1}{3} °$ . These phase shifts and others from the literature were used to study properties of the $α + α$ system in the center of mass energy range 1.50 to 14.74 MeV. First, an $R$ -matrix analysis was made of the $l = 4$ phase shifts; this analysis yields a resonance energy of 11.7 ± 0.4 MeV and a level width at resonance of 4.0 ± 0.4 MeV. Second, comparison was made of the $α + α$ phase shifts with results of previous resonating-group calculations, and this comparison shows good agreement with a calculation which includes one inelastic channel and a nucleon-nucleon repulsive core. Third, an $α + α$ potential model was constructed. This model contains an attractive potential obtained by folding Gaussian $α$ -particle densities together with a Yukawa-shaped direct part of a nucleon-nucleon potential and, in addition, contains phenomenological short-range repulsive components in the $l = 0$ and $l = 2$ states. The model reproduces the experimental phase shifts quite well when the Yukawa potential is taken to have a range corresponding to a two-pion mass.

NUCLEAR REACTIONS ${}^{4}{He} (α, α) {}^{4}{He}$ , $E = 18.00 - 29.50$ MeV; measured $σ (E; θ)$ ; deduced phase shifts $l = 0, 2, 4, 6$ . $R$ -matrix analysis $l = 4$ . Comparison with resonating-group calculations. Potential-model analysis.

Identification and lifetime determination of the $6^{+}$ member of the ground-state rotational band in ${}^{22}{Ne}$

L. K. Fifield, R. W. Zurmühle, and D. P. Balamuth

Phys. Rev. C 10, 1785 (1974) - Published 1 November, 1974

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The ${}^{19}F (α, p γ) {}^{22}{Ne}$ reaction was used to measure $p - γ$ angular correlations for the 6.31 and 6.34 MeV states in ${}^{22}{Ne}$ . The mean lifetimes of the two levels were determined to be 78 ± 15 fs (6.31 MeV) and $24_{- 17}^{+ 15}$ fs (6.34 MeV) using the same reaction and the Doppler-shift attenuation method. Unambiguous spin and parity assignments of $6^{+}$ and $4^{+}$ were obtained for the 6.31 and 6.34 MeV states, respectively. An earlier identification of the 6.34 MeV state as the $6^{+}$ member of the ground state rotational band is therefore incorrect. The $B (E 2)$ value of the 6.31 MeV ( $6^{+}$ ) → 3.36 MeV ( $4^{+}$ ) transition is in good agreement with recent large-basis shell model calculations, and the 6.31 MeV state may be identified as the $6^{+}$ member of the ground state rotational band of ${}^{22}{Ne}$ .

NUCLEAR REACTIONS ${}^{19}F (α, p γ)$ , $E_{α} = 12.0, 15.15$ MeV; measured $p - γ$ angular correlations, Doppler-shift attenuation. ${}^{22}{Ne}$ deduced levels, $τ$ , $J$ , $π$ , $B (Λ)$ .

Coupled-channel Born approximation and $l = 2 j$ dependence in ${}^{28}{Si} (d, p) {}^{29}{Si}$ from 10 to 18 MeV

W. R. Coker, Takeshi Udagawa, and G. W. Hoffmann

Phys. Rev. C 10, 1792 (1974) - Published 1 November, 1974

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We discuss the general problem of $j$ dependence in nuclear reactions, and evidence that $l = 2 j$ dependence seen in ( $d, p$ ) reactions is, at least in many cases, connected with the collective character of the target and residual nuclei in the reaction. To test this idea, we present analyses of three sets of data for ${}^{28}{Si} (d, p) {}^{29}{Si}$ , at 10, 13, and 18 MeV incident deuteron energy. These analyses are performed in terms of the coupled channel Born approximation (CCBA), and include inelastic excitations of vibrational character both in entrance and exit channels. It is shown that the observed $l = 2 j$ dependence, particularly for the 1.28 MeV ${\frac{3}{2}}^{+}$ and 2.03 MeV ${\frac{5}{2}}^{+}$ states in ${}^{29}{Si}$ , can be well explained by CCBA. Evidence is also presented that the 2.03 MeV ${\frac{5}{2}}^{+}$ and 2.43 MeV ${\frac{3}{2}}^{+}$ states have to a large extent the character [ ${}^{28}{Si} (2_{1}^{+}) \times {(s_{\frac{1}{2}})}_{n}$ ].

NUCLEAR REACTIONS ${}^{28}{Si} (d, p)$ , $E = 10.0, 13.0, 18.0$ MeV; calculated $σ (θ)$ with coupled channel Born approximation. $l = 2 j$ dependence of $σ (θ)$ accounted for.

Nuclear structure of calcium isotopes from inelastic $α$ scattering

M. J. A. de Voigt, D. Cline, and R. N. Horoshko

Phys. Rev. C 10, 1798 (1974) - Published 1 November, 1974

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Angular distributions were measured for elastic and inelastic $α$ scattering from ${}^{40}{Ca}$ at 24.0, 28.5, and 31.0 MeV, from ${}^{41}{Ca}$ at 24.0 MeV and from ${}^{43, 44}{Ca}$ at 25.5 MeV. Analyses in terms of distorted-wave Born-approximation and coupled-channel theory, employing a vibrational collective model form factor, yield inelastic transition strengths, and many new spin and parity assignments or restrictions for levels in ${}^{40, 41, 43, 44}{Ca}$ . The inelastic multipole transition strengths are in excellent agreement with known electromagnetic strengths. Quadrupole strengths are interpreted in terms of the coexistence model. The data imply that the ground-state excited-core admixtures to ${(f p)}^{n}$ spherical configurations are 4% in ${}^{48}{Ca}$ , 10% in ${}^{40, 41}{Ca}$ , 14% in ${}^{43}{Ca}$ , and 30% in ${}^{42, 44}{Ca}$ . The octupole inelastic strength is strong and mainly localized in the lowest $3^{-}$ state in ${}^{40}{Ca}$ , but becomes more fractionated and weaker with addition of neutrons and exhibits in ${}^{41}{Ca}$ characteristic weak-coupling fragmentation of the lowest $3^{-}$ state in ${}^{40}{Ca}$ . These results are consistent with previous observations that the structure of the ${}^{41}{Ca}$ ground state is with high purity a $1 f_{\frac{7}{2}}$ neutron coupled to the ${}^{40}{Ca}$ ground state.

NUCLEAR REACTIONS ${}^{40}{Ca} (α, α)$ , $E = 24.0, 28.5, 31.0$ MeV, ${}^{41}{Ca} (α, α)$ , $E = 24.0$ MeV, ${}^{43, 44}{Ca} (α, α)$ , $E = 25.5$ MeV, measured $σ (θ)$ , $E_{α}$ ; DWBA, coupled-channel analyses, ${}^{40, 41, 43, 44}{Ca}$ deduced levels, $J$ , $π$ , $B (I S, l) ↑$ for $l = 2, 3, 4, 5$ . Enriched targets. Coexistence model, deduced excited-core admixtures in ${}^{40, 41, 42, 43, 44, 48}{Ca}$ .

$E 0$ decay of the first excited $0^{+}$ states in ${}^{26}{Mg}$ and ${}^{30}{Si}$

J. C. Adloff, K. H. Souw, D. Disdier, F. Scheibling, P. Chevallier, and Y. Wolfson

Phys. Rev. C 10, 1819 (1974) - Published 1 November, 1974

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A new method was used to measure $E 0$ $π$ -decay branching ratios. A plastic scintillator pair spectrometer of high efficiency (3%) was used. It consists of four detectors. Two of them, very thin, select the electrons; the other two, thick, help to measure their energies. An annular counter ( $Ω = 0.10$ sr), working in coincidence with the spectrometer, allows the selection of the $π$ decay relevant to the $0^{+}$ excited state and the determination of its population yield. The reactions ${}^{23}{Na} (α, p) {}^{26}{Mg}$ (3.58 MeV)( $π$ ) and ${}^{27}{Al} (α, p) {}^{30}{Si}$ (3.79 MeV)( $π$ ) have been used to study the $E 0$ $π$ decay of the first excited $0^{+}$ state in ${}^{26}{Mg}$ and ${}^{30}{Si}$ . Pair spectra from the spectrometer were recorded in coincidence with protons in two-dimensional arrays. From the coincidence spectra the values for $\frac{Γ_{π}}{Γ}$ are found to be (5.1 ± 0.7) × $10^{- 3}$ and (2.6 ± 0.6) × $10^{- 3}$ , respectively, for ${}^{26}{Mg}$ (3.58 MeV) and ${}^{30}{Si}$ (3.79 MeV). When combined with the available lifetimes of these states, these ratios yield ${〈 M 〉}_{π} = (3.0 \pm 0.25)$ ${fm}^{2}$ ( ${}^{26}{Mg}$ and (1.4 ± 0.2) ${fm}^{2}$ ( ${}^{30}{Si}$ ) for the monopole matrix elements.

NUCLEAR REACTIONS ${}^{23}{Na} (α, p)$ , $E = 6.44$ MeV; ${}^{27}{Al} (α, p)$ , $E = 3.88$ MeV; ${}^{26}{Mg}$ , ${}^{30}{Si}$ measured $E 0$ branching ratio. Deduced $E 0$ matrix elements. Natural targets.

Systematics of the ( ${}^{3}{He}, p$ ) reaction on some $f$ -shell nuclei

Gerald Hardie, David Gloeckner, L. Meyer-Schützmeister, and T. H. Braid

Phys. Rev. C 10, 1829 (1974) - Published 1 November, 1974

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Using the Argonne split-pole magnetic spectrograph, the ${}^{43}{Ca} ({}^{3}{He}, p) {}^{45}{Sc}$ reaction was studied at $E ({}^{3}{He}) = 17$ MeV and with a range of angles from 7 to 55°. From the measured proton angular distributions the orbital angular momenta transferred ( $L_{n p}$ ) by the $n - p$ pair were obtained. In addition, at the same bombarding energy and at several angles, cross sections for $L_{n p} = 0 and 0 + 2$ were measured for the ( ${}^{3}{He}, p$ ) reaction with ${}^{46, 48, 50}{Ti}$ and ${}^{45}{Sc}$ targets. For these and other $f$ -shell nuclei, systematics of the cross sections for $L_{n p} = 0$ and the sum of the differential cross sections for $L_{n p} = 0 + 2$ will be discussed. In particular we found that for odd- $A$ targets the $L_{n p} = 0 + 2$ sums are significantly smaller than the average for even-even $f$ -shell targets. Two-particle spectroscopic amplitudes are calculated for transitions to ${}^{44}{Sc}$ , ${}^{45}{Sc}$ , ${}^{46}{Sc}$ , ${}^{47}{Ti}$ , ${}^{48}{Sc}$ , and ${}^{48}V$ using an ${(f_{\frac{7}{2}})}^{n}$ model and for transitions to ${}^{44}{Sc}$ , ${}^{45}{Sc}$ , ${}^{46}{Sc}$ , and ${}^{48}{Sc}$ using an ${(f_{\frac{7}{2}} p_{\frac{3}{2}})}^{n}$ model. Both models are based on an inert ${}^{40}{Ca}$ core. Zero-range distorted-wave Born-approximations calculations are then performed with these amplitudes. Reasonable agreement is found for the ratio of $L_{n p} = 0 + 2$ to $L_{n p} = 0$ strength with both models.

NUCLEAR REACTIONS ${}^{43}{Ca} ({}^{3}{He}, p)$ , ${}^{45}{Sc} ({}^{3}{He}, p)$ , ${}^{46, 48, 50}{Ti} ({}^{3}{He}, p)$ , $E = 17$ MeV; measured energy levels, $σ (θ)$ . Systematics of $σ (θ)$ for $L_{n p} = 0 and 0 + 2$ . Shell-model calculations.

( ${}^{16}O$ , ${}^{15}N$ ) and ( ${}^{12}C$ , ${}^{11}B$ ) reactions on ${}^{54}{Fe}$ and ${}^{62}{Ni}$ at $E ({}^{16}O) = 104$ MeV and $E ({}^{12}C) = 78$ MeV

F. D. Becchetti, B. G. Harvey, D. Kovar, J. Mahoney, and M. S. Zisman

Phys. Rev. C 10, 1846 (1974) - Published 1 November, 1974

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The ( ${}^{12}C$ , ${}^{11}B$ ) and ( ${}^{16}O$ , ${}^{15}N$ ) reactions on targets of ${}^{54}{Fe}$ and ${}^{62}{Ni}$ have been studied at bombarding energies far above the Coulomb barrier: $E ({}^{12}C) = 78$ MeV and $E ({}^{16}O) = 104$ MeV, respectively. The reaction mechanism appears to be direct and is adequately described with the distorted-wave Born approximation, provided recoil effects are included. A comparison of heavy-ion and light-ion analyses permits $j$ assignments to be made for some levels by utilizing the $j$ dependence of the heavy-ion reactions.

NUCLEAR REACTIONS ${}^{54}{Fe}$ ( ${}^{16}O$ , ${}^{15}N$ ), ${}^{62}{Ni}$ ( ${}^{16}O$ , ${}^{15}N$ ), $E = 104$ MeV; ${}^{54}{Fe}$ ( ${}^{12}C$ , ${}^{11}B$ ), ${}^{62}{Ni}$ ( ${}^{12}C$ , ${}^{11}B$ ), $E = 78$ MeV; measured $σ (E_{f}, θ)$ ; DWBA analysis; ${}^{55}{Co}$ and ${}^{63}{Cu}$ levels deduced $j$ values and spectroscopic factors. Resolution 100-200 keV.

Recoil corrections in distorted-wave Born approximation calculations of heavy-ion transfer reactions

J. S. Blair, R. M. DeVries, K. G. Nair, A. J. Baltz, and W. Reisdorf

Phys. Rev. C 10, 1856 (1974) - Published 1 November, 1974

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Various distorted-wave Born approximation (DWBA) theories which take only approximate account of recoil are assessed by comparing numerically their predictions to exact DWBA calculations of cross sections for heavy ion trnasfer. Of these the most successful for single nucleon transfer appears to be that of Baltz which treats recoil exactly through second order in the mass of the transferred particle. Also rather accurate are the first order theories of Baltz and Kahana and of Reisdorf. The theory of Buttle and Goldfarb which incorporates their approximate correction for recoil is useful near and below the Coulomb barrier, especially when there is good " $Q$ matching." Theories which completely neglect recoil are distinctly less reliable. None of the approximate theories here considered appear adequate for an example of $α$ particle transfer.

NUCLEAR REACTIONS ${}^{88}{Sr}$ ( ${}^{16}O$ , ${}^{15}N$ ), ${}^{30}{Si}$ ( ${}^{16}O$ , ${}^{15}N$ ), ${}^{40}{Ca}$ ( ${}^{16}O$ , ${}^{12}C$ ). Calculated $σ (θ)$ , comparison of exact and approximate finite range DWBA.

Level structure of ${}^{160}{Gd}$ from the ( $n, n^{'} γ$ ) reaction

S. A. Elbakr, I. J. van Heerden, D. R. Gill, N. Ahmed, W. J. McDonald, G. C. Neilson, and W. K. Dawson

Phys. Rev. C 10, 1864 (1974) - Published 1 November, 1974

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The energy levels of ${}^{160}{Gd}$ have been studied by the ( $n, n^{'} γ$ ) reaction. Deexcitation $γ$ rays were observed in a time-of-flight gated Ge(Li) detector at several neutron energies between $E_{n} = 1.10 and 2.32$ MeV. A level scheme for the ${}^{160}{Gd}$ nucleus is proposed. Previous spin and parity assignments for the 989 ( $2^{+}$ ) and 1149 ( $4^{+}$ ) keV levels were confirmed. New levels are proposed at 1058, 1351, 1378, 1381, 1436, 1569, 1587, and 1599 keV. Spin and parity assignments for previously known levels and for some new levels at 1058 ( $3^{+}$ ), 1071 ( $4^{+}$ ), 1149 ( $4^{+}$ ), 1378 ( $2^{+}$ ), 1381 ( $0^{+}$ ), and 1569 (1) keV have been determined by comparing the experimental cross sections with the predictions from the compound nuclear statistical model. A $J^{π}$ assignment is proposed for the 1225 ( $2^{+}$ ), 1290 ( $2^{-}$ ), 1351 (1, 2), 1464 ( $0^{+}$ ), and 1599 ( $0^{+}$ ) keV levels.

NUCLEAR REACTION ${}^{160}{Gd} (n, n^{'} γ)$ , $E_{n} = 1.10 - 2.32$ MeV, measured $E_{γ}$ , $σ ({\bar{E}}_{n}; E_{γ})$ . ${}^{160}{Gd}$ levels deduced, $J$ , $π$ , $γ$ branching. Enriched targets; Ge(Li) detector.

Independent fission yields of Rb and Cs from ${}^{238}U$ induced by fission-spectrum neutrons

Silvio J. Balestrini and Leon Forman

Phys. Rev. C 10, 1872 (1974) - Published 1 November, 1974

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The relative independent yields of Rb and Cs from ${}^{238}U$ fission induced by fission-spectrum neutrons have been determined by means of a mass spectrograph on line with a nuclear burst reactor. The spectrograph ion source is a tantalum oven containing a target of high purity ${}^{238}U$ in a graphite matrix. After irradiation, the radioactive fission products are deposited on the focal plane of the spectrograph and each mass position is analyzed quantitatively from its $β$ activities. Independent yields were calculated by normalizing the measurements using chain yield values and fractional independent yields that were calculated from recently measured cumulative yields for Kr and Xe. The results indicate a charge deviation from an unchanged charge distribution of 0.41 ± 0.07 nuclear charge units, a scaling factor of 1.27 for the number of neutrons associated with ${}^{238}U$ fission over the prompt number from thermal-neutron fission of ${}^{235}U$ for these fission products, and values of $σ$ for the isobaric charge distribution of 0.49 ± 0.04 and 0.60 ± 0.02 for Rb and Cs, respectively. An odd-even $Z$ effect is noticeable in that the fractional independent yields are generally lower by (20 ± 10)% for both Rb and Cs than the mean values estimated from a smooth theoretical model. The sum of the estimated independent yields for the Rb isotopes agrees within error with that for the isotopes of the complementary element Cs.

NUCLEAR REACTIONS ${}^{238}U (n, f)$ , $E = fission spectrum$ ; measured relative abundances; deduced independent fission yields, charge deviation, odd-even $Z$ effect. Mass spectrograph, burst reactor.

Levels of ${}^{56}{Ni}$

H. Nann and W. Benenson

Phys. Rev. C 10, 1880 (1974) - Published 1 November, 1974

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The ${}^{58}{Ni} (p, t) {}^{56}{Ni}$ reaction was studied at 40 and 45 MeV beam energy. An energy resolution of 10-25 keV permitted observation of 60 levels with excitation energy up to 10.5 MeV. Spin and parity are assigned to levels which were excited with characteristic angular distributions. These include $0^{+}$ states at 3.95, 5.00, 6.44, 7.91, 9.92, 9.99, and 10.02 MeV.

NUCLEAR REACTIONS ${}^{58}{Ni} (p, t)$ , $E_{p} = 40.0 and 45.5$ MeV; measured $σ (E_{t}, θ)$ ; enriched target. ${}^{56}{Ni}$ deduced levels, $L$ , $J$ , $π$ .

Transfer and compound-nucleus reactions that lead to the nuclei ${}^{245}{Cf}$ and ${}^{244}{Cf}$ : Interactions of ${}^{12}C$ with ${}^{239}{Pu}$ and ${}^{238}U$

R. L. Hahn, P. F. Dittner, K. S. Toth, and O. L. Keller

Phys. Rev. C 10, 1889 (1974) - Published 1 November, 1974

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The nuclear reactions ${}^{239}{Pu} ({}^{12}C, α 2 n - α 3 n)$ and ${}^{238}U ({}^{12}C, 5 n - 6 n)$ leading to the same radioactive products ${}^{245}{Cf}$ and ${}^{244}{Cf}$ have been studied by measuring excitation functions and recoil range and angular distributions. As expected, the U + C data are consistent with predictions for complete-fusion (CF) reactions; for example, the range distributions are Gaussian with mean values that increase with increasing bombarding energy, and the angular distributions are forward peaked in the laboratory system. The results for the Pu + C reactions differ markedly from those for U + C. The range distributions are asymmetric, with high energy tails, and have centroids that decrease monotonically with increasing ${}^{12}C$ energy, from 1.6 times the expected CF value at 67 MeV to 0.6 of the CF value at 97 MeV; the angular distributions are characterized by a maximum at ∼ 17° (lab) at energies well above the Coulomb barrier. The cross sections for the $Pu (C, α 2 n and α 3 n)$ reactions are much larger than those of the $Pu (C, 2 n to 4 n)$ reactions, also indicating that noncompound processes are involved in the production of the Cf nuclides, since evaporation of charged particles is expected to be negligible in such heavy nuclei. All of these results for the ( $C, α xn$ ) reactions are consistent with models of transfer reactions in which an aggregate is transferred from the projectile to the target nucleus, followed by evaporation of neutrons from the resulting heavy nucleus. In particular, the average recoil energies and angles are reproduced reasonably well by models that consider the kinematics of the transfer process.

NUCLEAR REACTIONS ${}^{239}{Pu} ({}^{12}C, α 2 n and α 3 n)$ and ${}^{238}U ({}^{12}C, 5 n and 6 n)$ . $E = 63 - 97$ MeV; measured $σ (E)$ , recoil range and angular distributions for ${}^{245}{Cf}$ and ${}^{244}{Cf}$ ; deduced average values of ranges, recoil energies $E_{R}$ and angles of emission $θ_{R}$ ; calculated $E_{R}$ and $θ_{R}$ with models of transfer reactions.

Neutron resonance spectroscopy: ${}^{154, 158, 160}{Gd}$

F. Rahn, H. S. Camarda, G. Hacken, W. W. Havens, Jr., H. I. Liou, and J. Rainwater

Phys. Rev. C 10, 1904 (1974) - Published 1 November, 1974

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Neutron time of flight spectroscopy measurements were made for a range of sample thickness on the even separated Gd isotopes $A = 154, 158, and 160$ . These include transmission measurements using 200 and 40 m flight paths and self-indication measurements using a 40 m flight path. Resonance parameters were obtained for 48 levels to 1 keV for ${}^{154}{Gd}$ and for 95 and 56 levels to 10 keV for ${}^{158}{Gd}$ and ${}^{160}{Gd}$ . The experimental $s$ -wave strength functions were $10 {}^{4}S_{0} = (2.0 \pm 0.3), (1.5 \pm 0.2), and (1.8 \pm 0.4)$ , respectively. For ${}^{160}{Gd}$ , the $p$ strength function is $10 {}^{4}S_{1} \approx 1.7 \pm 0.3$ . Essentially complete $s$ -wave populations were obtained for the first 19 levels in ${}^{154}{Gd}$ with $〈 D 〉 = 14.5 \pm 1.5$ eV and $Δ_{\exp} = 0.22$ (vs $Δ_{DM} = 0.28 \pm 0.11$ ); 47 levels in ${}^{158}{Gd}$ with $〈 D 〉 = 86 \pm 4$ eV and $Δ_{\exp} = 0.29$ (vs $Δ_{DM} = 0.38 \pm 0.11$ ); and 20 levels in ${}^{160}{Gd}$ with $〈 D 〉 = 202 \pm 20$ and $Δ_{\exp} = 0.32$ (vs $Δ_{DM} = 0.30 \pm 0.11$ ). Comparison of the observed $Γ_{n}^{0}$ distributions with the Porter-Thomas theory and the observed level spacings with the Wigner theory and other statistical orthogonal ensemble tests gave good results for the energy intervals over which complete $s$ populations were observed. The average radiation widths were $〈 Γ_{γ} 〉 = 88$ meV determined from $n = 25$ levels in ${}^{154}{Gd}$ , $〈 Γ_{γ} 〉 = 105$ meV ( $n = 27$ ) in ${}^{158}{Gd}$ and $〈 Γ_{γ} 〉 = 11$ meV ( $n = 4$ ) in ${}^{160}{Gd}$ .

NUCLEAR REACTIONS ${}^{154, 158, 160}{Gd} (n, n)$ , ( $n, γ$ ), $E = 0 - 10$ keV; measured $σ_{t} (E)$ ; deduced $E_{0}$ , $Γ_{n}$ , $Γ_{γ}$ , $S_{0}$ , $〈 D_{0} 〉$ , $S_{1}$ .

Neutron resonance spectroscopy. XVI. ${}^{113}{In}$ , ${}^{115}{In}$

G. Hacken, H. I. Liou, H. S. Camarda, W. J. Makofske, F. Rahn, J. Rainwater, M. Slagowitz, and S. Wynchank

Phys. Rev. C 10, 1910 (1974) - Published 1 November, 1974

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Results of neutron time of flight spectroscopy measurements for natural indium and separated ${}^{115}{In}$ , using the Nevis synchrocyclotron, are given. Transmission and self-indication measurements were made for a range of natural indium sample thicknesses and for a sample of 99.5% enriched ${}^{115}{In}_{2}$ $O_{3}$ . Resonance parameters $E_{0}$ and $g Γ_{n}^{0}$ are given to 2 keV. Part of the isotope assignment was made with the aid of ${}^{113}{In}$ raw capture data taken at Geel by C. Coceva. Some $Γ_{γ}$ values were also obtained, from which we estimate $〈 Γ_{γ} 〉$ to be 75 meV for ${}^{113}{In}$ (based on three levels), and 85 meV for ${}^{115}{In}$ (15 levels). The $l = 0$ strength function for ${}^{115}{In}$ is $10 {}^{4}S_{0} = 0.26 \pm 0.03$ . Comparison of the ${(g Γ_{n}^{0})}^{\frac{1}{2}}$ distribution with Porter-Thomas theory for ${}^{115}{In}$ shows that many $p$ levels are observed. An estimate of the level detection sensitivity and a Bayes's theorem analysis allow a determination of the $p$ strength function and its uncertainty: $10 {}^{4}S_{1} = 2.7 + 1.0 or - 0.7$ for ${}^{115}{In}$ . We find $〈 D 〉 = (9.4 \pm 0.2)$ eV for ${}^{115}{In}$ $s$ levels.

NUCLEAR REACTIONS ${}^{113, 115}{In} (n, n)$ , ( $n, γ$ ), $E = 0 - 2$ keV; measured $σ_{t}$ ( $E$ ); deduced $E_{0}$ , $g Γ_{n}$ , $Γ_{γ}$ , $S_{0}$ , $〈 D_{0} 〉$ , $S_{1}$ .

Derivation of a coupling potential for Coulomb-nuclear interference effects

V. Oberacker, H. Holm, and W. Scheid

Phys. Rev. C 10, 1917 (1974) - Published 1 November, 1974

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A collective coupling potential for surface vibrations is calculated from an extended liquid drop model. It describes Coulomb and nuclear excitations. Applying the potential to the reaction ${}^{58}{Ni}$ ( ${}^{16}O$ , ${}^{16}{O'}$ ) ${}^{58}{N i *}$ , we obtain a good agreement with recent experimental data.

NUCLEAR REACTIONS ${}^{58}{Ni}$ ( ${}^{16}O$ , ${}^{16}O$ ) ${}^{58}{N i *}$ , $E = 34 - 58$ MeV; derivation of coupling potentials; calculated $σ (E)$ .

Half-life of the 257 keV $1^{+}$ → $4^{-}$ transition in ${}^{90}{Nb}$

W. J. Courtney, C. I. Delaune, J. W. Nelson, and J. D. Fox

Phys. Rev. C 10, 1922 (1974) - Published 1 November, 1974

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The half-life of the 382 keV $1^{+}$ state in ${}^{90}{Nb}$ has been determined by detecting the 257 keV conversion electron decay following the ${}^{90}{Zr} (p, n) {}^{90}{Nb}$ reaction induced by a chopped proton beam. The value obtained is 6.3 ± 0.2 ms, in good agreement with two earlier measurements but different from the value adopted in 1970 in Nuclear Data Tables.

NUCLEAR REACTIONS ${}^{90}{Zr} (p, n)$ , $E = 8.0$ MeV; ${}^{90}{Nb}$ detected ce, measured $T_{\frac{1}{2}}$ .

Recoil properties of ${}^{22}{Na}$ and ${}^{24}{Na}$ produced in the interaction of ${}^{27}{Al}$ with 3- to 300-GeV protons

E. P. Steinberg and L. Winsberg

Phys. Rev. C 10, 1925 (1974) - Published 1 November, 1974

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Values of $2 W (F + B)$ and $\frac{F}{B}$ were determined for ${}^{22}{Na}$ and ${}^{24}{Na}$ in irradiations of Al targets with protons of 3, 6, 9, 11.5, 200, and 300 GeV. The values of $2 W (F + B)$ were found to be constant within experimental error from 3 to 300 GeV for both ${}^{22}{Na}$ and ${}^{24}{Na}$ . The $\frac{F}{B}$ values for both nuclides decreased about 20% over the same energy range.

NUCLEAR REACTIONS ${}^{27}{Al}$ ( $p, spallation$ ) ${}^{22}{Na}$ , ${}^{24}{Na}$ ; $E = 3, 6, 9, 11.5, 200, and 300$ GeV; measured $2 W (F + B)$ and $\frac{F}{B}$ .

${}^{87}{Sr} (d, p) {}^{88}{Sr}$ reaction

Kamal K. Seth, Kurt A. Buzard, J. Picard, and G. Bassani

Phys. Rev. C 10, 1928 (1974) - Published 1 November, 1974

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Neutron particle-hole states in ${}^{88}{Sr}$ have been studied by means of the reaction ${}^{87}{Sr} (d, p) {}^{88}{Sr}$ at $E_{d} = 12$ MeV. It has been determined that the earlier reported transitions to presumed states at 4744 and 5780 keV in ${}^{88}{Sr}$ arise mainly from transition to the ground state and the first excited state in ${}^{89}{Sr}$ . Spectroscopic strengths for states of the multiplets [ ${g_{\frac{9}{2}}}^{- 1} d_{\frac{5}{2}}$ ] and [ ${g_{\frac{9}{2}}}^{- 1} s_{\frac{1}{2}}$ ] have been determined by detailed distorted-wave Born-approximation analysis. $J^{π}$ assignments are suggested on the basis of sum rules and comparison with other experiments. Matrix elements for two-particle effective interactions are derived.

NUCLEAR REACTIONS ${}^{87}{Sr} (d, p)$ , $E = 12$ MeV; measured $σ (θ)$ deduced level energies, $J^{π}$ ; deduced two body matrix elements; enriched targets.

Anomalies in the ${}^{72}{Ge} (α, n) {}^{75}{Se}$ reaction near isobaric analog resonances in ${}^{76}{Se}$

A. J. Elwyn, J. E. Monahan, J. F. Lemming, J. Rapaport, and M. Sample

Phys. Rev. C 10, 1939 (1974) - Published 1 November, 1974

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Anomalies in the excitation function of the reaction ${}^{72}{Ge} (α, n) {}^{75}{Se}$ are compared with isobaric analog resonances observed in the ${}^{75}{As} (p, n) {}^{75}{Se}$ reaction. The results are consisted with the interpretation that the same analog resonance is populated in both reactions. Since the ( $α, n$ ) reaction through isobaric analog states is isospin forbidden in both entrance and exit channels, these results imply some isospin-breaking mechanism for the excitation of analog resonances via $α$ and/or neutron channels.

NUCLEAR REACTIONS ${}^{72}{Ge} (α, n)$ , $E = 7.735 - 8.355$ MeV; measured 111 and 286 keV $γ$ -ray yields; enriched target. ${}^{75}{As} (p, n)$ , $E = 2.91 - 3.59$ ; measured total 0° neutron yield. Deduced properties IAR in ${}^{76}{Se}$ .

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