Recent Articles

Levels of ${}^{38}K$ : The ${}^{40}{Ca} (d, α)$ , ${}^{40}{Ca} (d, α γ)$ , and ${}^{36}{Ar} ({}^{3}{He}, p γ)$ reactions

W. K. Collins, D. S. Longo, J. F. Mateja, P. R. Chagnon, E. D. Berners, G. F. Neal, C. P. Browne, P. L. Jolivette, A. A. Rollefson, and J. D. Goss

Phys. Rev. C 11, 1925 (1975) - Published 1 June, 1975

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Precise level energies in ${}^{38}K$ have been measured up to the region of 6 MeV in excitation with our 100-cm broad-range magnetic spectrograph and the ${}^{40}{Ca} (d, α)$ reaction. With a Ge(Li) detector, $γ$ -ray energies were measured in the ${}^{40}{Ca} (d, α γ)$ and ${}^{36}{Ar} ({}^{3}{He}, p γ)$ reactions. Some 79 states have been identified in this region of excitation, approximately 30 of which have not previously been reported. Uncertainties in excitation energies are 1 to 3.5 keV. Branching ratios for levels up to 5.2 MeV were determined, and particle- $γ$ angular correlations were measured with the ${}^{36}{Ar} ({}^{3}{He}, p γ)$ reaction. The mean lives of some levels in ${}^{38}K$ excited in the ${}^{40}{Ca} (d, α γ)$ reaction at $E_{d} = 7.84$ MeV have been determined using the Dopplershift attenuation method. The following mean lifetimes were deduced (excitation energy in keV, lifetime in fs): 3431, < 170; 3615, $700_{- 310}^{+ 850}$ ; 3668, 95 ± 55; 3688, $400_{- 120}^{+ 160}$ ; 3702, > 1100; and 4333, $350_{- 250}^{+ 700}$ . The angular correlations, with the lifetimes and previous information, lead to the following assignments to the 3431-, 3615-, and 3688-keV levels, respectively: $J^{π} = (2), (3^{-} or 5^{-}), (3)$ , where parentheses indicate assignments dependent upon unproven assignments to other levels from the literature. The observed decays further imply $J = (1, 2)$ for both the 3857- and 4214-keV levels. Clarifications of several ambiguous and erroneous level identifications in the literature are offered.

NUCLEAR REACTIONS ${}^{40}{Ca} (d, α)$ , $E = 7.84 - 16.0$ MeV, ${}^{36}{Ar} ({}^{3}{He}, p)$ , $E = 8.34$ MeV; measured $E_{α}$ , $E_{γ}$ , $α γ$ , $α γ (θ)$ , $p γ$ , $p γ (θ)$ , $γ$ branching, Doppler-shift attenuation. ${}^{38}K$ deduced levels, $J$ , $π$ , $T$ , $τ$ , $δ$ .

Study of the ${}^{40}{Ar} ({}^{3}{He}, d) {}^{41}K$ reaction

L. R. Medsker, H. T. Fortune, S. C. Headley, and J. N. Bishop

Phys. Rev. C 11, 1937 (1975) - Published 1 June, 1975

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The ${}^{40}{Ar} ({}^{3}{He}, d) {}^{41}K$ reaction has been studied at a bombarding energy of 18 MeV. The ${}^{40}{Ar}$ target was contained in a gas cell with no entrance window. Excitation energies and angular distributions were obtained for 80 levels below $E_{x} = 7.8$ MeV in ${}^{41}K$ . A distorted-wave analysis was used to determine $l$ values and spectroscopic strengths. The proton configurations of ${}^{41}K$ are examined in comparison with previous data on reactions and radioactive decay.

NUCLEAR REACTIONS ${}^{40}{Ar} ({}^{3}{He}, d)$ , $E = 18$ MeV; measured $σ (E_{d}, θ)$ ; deduced ${}^{41}K$ levels, $l$ , $j$ , $G_{lj}$ .

Lifetime of the 563-keV level of ${}^{24}{Na}$

E. H. du Marchie van Voorthuysen, A. S. Keverling Buisman, A. Becker, and Ph. B. Smith

Phys. Rev. C 11, 1943 (1975) - Published 1 June, 1975

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The lifetime of the 563-keV level of ${}^{24}{Na}$ has been measured by means of the recoil-distance method. In the geometry used, the "stopped" and "shifted" peaks lie above and below the $K$ edge of bismuth. The use of a bismuth absorber of suitable thickness essentially eliminated the stopped peak from the spectrum, leading to an exponential function for the transmitted intensity as a function of the recoil distance. The mean life was measured as $τ_{m} = 62 \pm 8$ ps.

NUCLEAR REACTIONS ${}^{26}{Mg} (d, α γ)$ , $E = 4.5$ MeV, measured $α γ$ coin, $T_{\frac{1}{2}}$ recoil distance; deduced $B (Λ)$ .

High-spin states of ${}^{28}{Al}$

R. M. Freeman, F. Haas, A. R. Achari, and R. Modjtahed-Zadeh

Phys. Rev. C 11, 1948 (1975) - Published 1 June, 1975

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Stripping angular distributions for the ${}^{27}{Al} (d, p) {}^{28}{Al}$ reaction, lifetime and branching ratio measurements demonstrate the similarity between the configurations of the 4033 and 5165 keV levels of ${}^{28}{Al}$ . The 5165 keV level is probably the $J^{π} = 6^{-}$ state predominantly of configuration ${d_{\frac{5}{2}}}^{- 1}$ Lifetime and branching ratio measurements are also reported for the 2581 keV level for which $J^{π} = 5^{+}$ had been proposed.

NUCLEAR REACTIONS ${}^{27}{Al} (d, p)$ , $E = 12.32$ MeV, measured $σ (θ)$ , DWBA analysis; $E = 3.14$ MeV, measured $p - γ$ coincidences, deduced ${}^{28}{Al}$ level branchings and lifetimes.

Threshold pion production in pion - nucleus collisions: A simple estimate

Ronald Rockmore

Phys. Rev. C 11, 1953 (1975) - Published 1 June, 1975

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The Goldhaber-Teller model generalized to spin-isospin vibrations is used to provide a simple estimate for the total cross section for threshold pion production in pion-nucleus collisions ( $π^{-} A_{Z} \to π^{-} π^{+} A_{Z - 1}$ ) in the case of nuclei with $N = Z$ . Cross sections are calculated using the threshold approximant to the production amplitude for single nucleons consisting of pion pole plus contact terms alternately derived from the phenomenological Lagrangian theory and the current-commutator theory of multiple-pion production. The threshold approximant in the latter theory fits the experimental pion-production data on protons poorly and, in the case of ${}^{4}{He}$ , the lightest target nucleus we consider, that theory predicts cross sections about a factor of 2 smaller than those similarly calculated with phenomenological Lagrangian input. On the other hand, for ${}^{12}C$ and ${}^{16}O$ , the predictions of the alternative threshold theories are in essential agreement. In the case of the current-commutator theory, the Goldhaber-Teller predictions for ${}^{4}{He}$ and ${}^{16}O$ are consistent with those of the particle-hole model obtained earlier by Eisenberg after quadrupling his calculated values to compensate for an omitted factor of 2 in his production amplitude. While the cross sections for the ( $π, 2 π$ ) reaction in nuclei are still expected to be quite small, the prospect for their accessibility seems reasonably improved.

NUCLEAR REACTIONS ${}^{4}{He} (π^{-}, π^{-} π^{+})$ , ${}^{12}C (π^{-}, π^{-} π^{+})$ , ${}^{16}O (π^{-}, π^{-} π^{+})$ ; threshold pion production cross section calculated with a spin-isospin-generalized Goldhaber-Teller model with phenomenological Lagrangian and current-commutator inputs and compared to particle-hole model predictions.

Mass of ${}^{9}{Li}$

E. Kashy, W. Benenson, D. Mueller, R. G. H. Robertson, and D. R. Goosman

Phys. Rev. C 11, 1959 (1975) - Published 1 June, 1975

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New precise determinations of the ${}^{9}{Li}$ mass excess by observation of the ${}^{10}{Be} (d, {}^{3}{He}) {}^{9}{Li}$ reaction and by analysis of ${}^{7}{Li} (t, p) {}^{9}{Li}$ data have yielded a value of 24.9554±0.0020 MeV. This value, which is 10 keV lower than previous results, makes a significant reduction in the cubic coefficient of the isobaric multiplet mass equation for the $A = 9$ ground state quartet. The new value of $d$ , 5.8±1.5 keV, is considerably closer to theoretical estimates.

NUCLEAR REACTIONS ${}^{10}{Be} (d, {}^{3}{He})$ and ${}^{7}{Li} (t, p)$ . Measured ${}^{9}{Li}$ mass. Deduced coefficients of IMME for $A = 9$ quartets.

Study of the ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) reactions

W. R. Wharton and P. T. Debevec

Phys. Rev. C 11, 1963 (1975) - Published 1 June, 1975

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We have measured and analyzed angular distributions of ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) reactions at $E_{lab} \sim 34$ MeV on targets between $A = 6$ and $A = 48$ . The analysis indicates that the ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) reaction has sizable contributions from multistep processes except possibly for transitions of zero angular momentum transfer ( $L = 0$ ) near closed shells. The $L = 0$ partial cross sections of the ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) reaction are correlated with the known Gamow-Teller strength obtained from $β$ -decay measurements, except for a smoothly target-dependent uncorrelated factor which makes the ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) $L = 0$ cross sections too large in the middle of the $s - d$ shell. The ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) reactions should be useful in studying the distribution of Gamow-Teller strength in nuclei.

NUCLEAR REACTIONS ${}^{18}O$ ( ${}^{6}{Li}$ , ${}^{6}{He}$ ), ${}^{30}{Si}$ ( ${}^{6}{Li}$ , ${}^{6}{He}$ ), ${}^{34}S$ ( ${}^{6}{Li}$ , ${}^{6}{He}$ ), $E = 32$ MeV; ${}^{42, 44, 48}{Ca}$ ( ${}^{6}{Li}$ , ${}^{6}{He}$ ), $E = 34$ MeV; measured $σ (E_{He}, θ)$ , systematic DWBA analysis includes ${}^{6}{Li}$ ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) and ${}^{26}{Mg}$ ( ${}^{6}{Li}$ , ${}^{6}{He}$ ).

Transient field at nitrogen nuclei recoiling in iron and the magnetic moment of the ${}^{15}N$ first excited state

M. Forterre, J. Gerber, J. P. Vivien, M. B. Goldberg, K. -H. Speidel, and P. N. Tandon

Phys. Rev. C 11, 1976 (1975) - Published 1 June, 1975

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Precession measurements have been performed on nuclear-excited nitrogen ions recoiling in magnetized iron employing the implantation perturbed-angular-correlation technique. The transient magnetic field, calibrated with the ${}^{16}N$ ( $1^{-}$ ) state, was found to be enhanced by a factor of 2.1(5) over the empirically adjusted Lindhard-Winther prediction. A negative sign was determined for this $g$ factor and a value of $g = + 0.9 (3)$ for that of the ${}^{15}N ({\frac{5}{2}}^{+})$ state.

NUCLEAR REACTIONS ${}^{13, 14}C ({}^{3}{He}, p)$ , $E_{{}^{3}{He}} = 2 - 4$ MeV; measured $W (θ_{γ})$ ${}^{15, 16}N$ levels, recoil in magnetized iron, deduced $H_{transient}$ , $g$ .

${}^{41}K ({}^{3}{He}, t)$ reaction at 25 MeV

M. Stautberg Greenwood, M. Pluta, L. R. Greenwood, and N. Anantaraman

Phys. Rev. C 11, 1983 (1975) - Published 1 June, 1975

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Angular distributions for the ${}^{41}K ({}^{3}{He}, t) {}^{41}{Ca}$ reaction were measured for 35 states up to 7.61-MeV excitation energy in ${}^{41}{Ca}$ . $L$ values were deduced from a microscopic distorted-wave Born-approximation analysis. Of especial interest was the comparison of $T_{<}$ and $T_{>}$ states with the same shell-model configurations. The ${\frac{7}{2}}^{-}$ ground state and ${\frac{7}{2}}^{-}$ excited analog state at 7.12 MeV were both fitted by $L = 3 + 5$ , although the data exhibited more structure and peaked at a more forward angle than the DW calculation. Whereas the angular distribution of the ${\frac{3}{2}}^{+}$ analog state at 5.822 MeV was described principally by $L = 0$ , the angular distribution of the ${\frac{3}{2}}^{+}$ antianalog state at 2.005 MeV was fitted by $L = 2$ . Evidence is presented to show that the $L = 2$ character of the angular distribution of the antianalog state is due to the $f_{\frac{7}{2}} \to f_{\frac{7}{2}}$ transition with $L = 2$ , $S = 0$ . The 2.68- and 3.394-MeV states with $J^{π} = {\frac{1}{2}}^{+}$ , excited by $l_{n} = 0$ in ${}^{42}{Ca} (p, d)$ , can be obtained by either $f_{\frac{7}{2}} \to f_{\frac{7}{2}}$ or $s_{\frac{1}{2}} \to d_{\frac{3}{2}}$ transitions, both with $L = 2$ , $S = 0$ . However, the 2.68-MeV state was not observed, suggesting that the effects of the two competing transitions enhance the 3.394-MeV state but may tend to cancel for the 2.68-MeV state. The 4.098-MeV state ( $J^{π} = {\frac{5}{2}}^{+}$ ) was strongly excited and appears to arise from the $f_{\frac{7}{2}} \to f_{\frac{7}{2}}$ transition with $L = 2$ and $S = 0 or 1$ . The transition to the 2.875-MeV level, known to have $l_{n} = 4$ in ${}^{40}{Ca} (d, p)$ , was assigned $L = 2$ , thus strongly suggesting $J^{π} = {\frac{7}{2}}^{+}$ since spin-flip excitation is expected to be weak.

NUCLEAR REACTIONS ${}^{41}K ({}^{3}{He}, t)$ , $E = 25$ MeV; measured $σ (θ)$ . Enriched targets, DWBA analysis. ${}^{41}{Ca}$ deduced levels, $l$ , $π$ , IAS.

${}^{89}Y ({}^{3}{He}, t)$ reaction at 25 MeV

M. Stautberg Greenwood, M. Pluta, N. Anantaraman, and L. R. Greenwood

Phys. Rev. C 11, 1995 (1975) - Published 1 June, 1975

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Nineteen angular distributions were obtained for the ${}^{89}Y ({}^{3}{He}, t) {}^{89}{Zr}$ reaction at 25 MeV. The angular distribution of the 0.59-MeV state, thought previously to be the antianalog state, is characterized by $L = 2$ with spin-flip. This indicates the presence of a configuration, other than the antianalog configuration, in the wave function of the 0.59-MeV state. Arguments are presented to show that the $g_{\frac{9}{2}} \to g_{\frac{9}{2}}$ transition with $L = 2$ , $S = 1$ is responsible for the excitation of this state. Angular distributions leading to the ground state, the 1.514-, 2.784-, and 2.932-MeV states are very similar. Since the ground state and the 1.514-MeV state have $J^{π} = {\frac{9}{2}}^{+}$ , this suggests that the other states also have $J^{π} = {\frac{9}{2}}^{+}$ . The angular distribution leading to the ground state was not satisfactorily fitted by distorted-wave calculations, since the forward peaking corresponded to $L = 2$ , rather than to the allowed $L = 3$ and $L = 5$ . The structure of the ${\frac{9}{2}}^{+}$ states was investigated in terms of the coupling of a $g_{\frac{9}{2}}$ neutron hole to the $0^{+}$ states in ${}^{90}{Zr}$ .

NUCLEAR REACTIONS ${}^{89}Y ({}^{3}{He}, t)$ , $E = 25$ MeV; measured $σ (θ)$ . DWBA analysis. ${}^{89}{Zr}$ deduced levels, $l$ , $π$ .

( $π, d$ ) reaction for small incident pion energies

Robert A. Eisenstein and Gerald A. Miller

Phys. Rev. C 11, 2001 (1975) - Published 1 June, 1975

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we suggest that the reaction $π + A \to d + B$ provides a useful probe of nuclear structure. A model in which the pion is absorbed on a single nucleon is used to calculate the cross sections in a plane wave approximation. Results are presented for ${}^{18}O$ and ${}^{118}{Sn}$ targets. The high momentum transfer nature of this reaction leads to considerable sensitivity to the dineutron wave function on which the pion is absorbed.

NUCLEAR REACTIONS ${}^{18}O (π, d)$ , ${}^{118}{Sn} (π, d)$ , $E = 50 - 100$ MeV; theoretical predictions of cross sections; plane wave analysis.

$E 2$ and $E 4$ transition moments in ${}^{172}{Yb}$ , ${}^{174}{Yb}$ , and ${}^{176}{Yb}$

H. J. Wollersheim, W. Wilcke, and T. W. Elze

Phys. Rev. C 11, 2008 (1975) - Published 1 June, 1975

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Electric quadrupole and hexadecapole transition matrix elements in the ground-state rotational bands of ${}^{172}{Yb}$ , ${}^{174}{Yb}$ , and ${}^{176}{Yb}$ were measured in precise Coulomb excitation experiments with 13 MeV $α$ particles. The results are $〈 2^{+} ∥ M (E 2) ∥ 0^{+} 〉 = 2.456 \pm 0.012 e b, 2.439 \pm 0.012 e b, 2.325 \pm 0.018 e b$ and $〈 4^{+} ∥ M (E 4) ∥ 0^{+} 〉 = {0.22}_{- 0.18}^{+ 0.12} e b^{2}, {0.21}_{- 0.18}^{+ 0.14} e b^{2}, {0.28}_{- 0.20}^{+ 0.11} e b^{2}$ for ${}^{172}{Yb}$ , ${}^{174}{Yb}$ , and ${}^{176}{Yb}$ , respectively. Model-dependent charge deformation parameters, $β_{2}$ and $β_{4}$ , are deduced from the measured transition moments.

NUCLEAR REACTIONS ${}^{172, 174, 176}{Yb} (α, α^{'})$ , $E = 13$ MeV; measured $σ (E_{α^{'}}; θ = 160 °)$ ; deduced $〈 2^{+} ∥ M (E 2) ∥ 0^{+} 〉$ , $〈 4^{+} ∥ M (E 4) ∥ 0^{+} 〉$ . Deduced charge deformation parameters, $β_{2}$ and $β_{4}$ .

Proton-induced reactions on ${}^{89}Y$

J. R. Comfort, A. M. Nathan, W. J. Braith waite, and J. R. Duray

Phys. Rev. C 11, 2012 (1975) - Published 1 June, 1975

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The reactions ${}^{89}Y (p, t) {}^{87}Y$ , ${}^{89}Y (p, d) {}^{88}Y$ , and ${}^{89}Y (p, α) {}^{86}{Sr}$ are studied with 27.8-MeV protons and solid-state-detector telescopes. A recent revision of the mass of ${}^{87}Y$ is confirmed. Angular distributions are obtained for the observed states. Several new levels are found in ${}^{87}Y$ . The states at 0.98, 1.85, and 2.09 MeV are assigned $J^{π} = {\frac{3}{2}}^{-}, {\frac{1}{2}}^{-}, and {\frac{3}{2}}^{-}$ , respectively. In ${}^{89}Y$ , the existence of two low-spin states of opposite parity is established at 0.705 MeV. Distorted-wave Born-approximation (DWBA) calculations are carried out for the ( $p, d$ ) and ( $p, t$ ) data. Good fits to the data are obtained for the ( $p, d$ ) reaction, but the $l = 4$ and $l = 1$ summed strengths deviate in opposite directions from the sum rules. Poor fits are obtained for $L = 0$ transitions in the ( $p, t$ ) reaction on ${}^{89}Y$ and the experimental $L = 2$ angular distributions show features that are not reproduced by the DWBA. Multistep contributions are suggested. The data for the ( $p, α$ ) reaction show some evidence for direct-reaction processes, but DWBA calculations cannot be carried out.

NUCLEAR REACTIONS ${}^{89}Y (p, d)$ , ( $p, t$ ), ( $p, α$ ), $E = 27.8$ MeV; measured $σ (E, θ)$ , $θ = 9 - 50 °$ , $Δ θ = 3 - 4 °$ , resolution 35-60 keV; deduced ${}^{87}Y$ - ${}^{88}Y$ mass difference, ${}^{87, 88}Y$ , ${}^{86}{Sr}$ levels; DWBA analysis, deduced $S$ for ${}^{88}Y$ .

Neutron resonance spectroscopy: ${}^{177}{Hf}$

H. I. Liou, J. Rainwater, G. Hacken, and U. N. Singh

Phys. Rev. C 11, 2022 (1975) - Published 1 June, 1975

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High resolution neutron time of flight spectroscopy measurements were made for a sample enriched in ${}^{177}{Hf}$ using the Columbia University Nevis synchrocyclotron. The measurements used the 202.05 m flight path for transmission measurements and the 39.37 m flight path for capture measurements. We obtained ( $E_{0}$ , $g Γ_{n}^{0}$ ) resonance parameters for 176 levels in ${}^{177}{Hf}$ to 700 eV and 12 levels in ${}^{178}{Hf}$ to 720 eV. We also obtained $Γ_{γ}$ values for 25 levels in ${}^{177}{Hf}$ , givirg $〈 Γ_{γ} 〉 = 65$ meV. The $s$ wave strength function for ${}^{177}{Hf}$ is found to be (2.70 ± 0.25). Most $s$ levels were detected to 100 eV, but many were missed above 100 eV. An analysis favors $〈 D_{0} 〉 = (2.22 \pm 0.13)$ eV for the "true" $s$ level spacing in ${}^{177}{Hf}$ . The results to 100 eV are in reasonable agreement with predictions for statistical orthogonal population ensembles.

NUCLEAR REACTIONS ${}^{177}{Hf} (n, n)$ , ( $n, γ$ ), $E = 3 - 700$ eV; measured $σ_{t} (E)$ ; deduced $E_{0}$ , $g Γ_{n}^{0}$ , $Γ_{γ}$ , $S_{0}$ , $〈 D_{0} 〉$ , $\frac{S_{0} (J = 4)}{S_{0} (J = 3)}$ ; orthogonal ensemble tests.

Spectroscopy of ${}^{52}{Mn}$ from the ${}^{54}{Fe} (p, {}^{3}{He})$ reaction at 40.2 MeV

A. Guichard, W. Benenson, and H. Nann

Phys. Rev. C 11, 2027 (1975) - Published 1 June, 1975

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The ${}^{54}{Fe} (p, {}^{3}{He})$ reaction has been studied at 40.2 MeV between 6° and 60°. Assignments of $L$ transfers have been made with distorted-wave Born approximation calculations. These results are compared with other two-nucleon transfer data and theoretical shell-model calculations.

NUCLEAR REACTIONS ${}^{54}{Fe} (p, {}^{3}{He})$ , $E_{p} = 40.2$ MeV; measured $σ (E_{{}^{3}{He}}, θ)$ ; enriched target. Deduced energies, $L$ values of ${}^{52}{Mn}$ levels.

Decay of the 1.7-h isomer of ${}^{186}{Ir}$

S. W. Yates, J. C. Cunnane, and P. J. Daly

Phys. Rev. C 11, 2034 (1975) - Published 1 June, 1975

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Levels in ${}^{186}{Os}$ populated in the decay of 1.7-h ${}^{186}{Ir}$ have been studied by high-resolution $γ$ -ray singles and $γ - γ$ coincidence spectroscopy. Many $γ$ rays have been assigned to this decay and several new levels in ${}^{186}{Os}$ have been established. On the basis of the observed decay properties and level systematics, a spin-parity assignment of $2^{-}$ and the Nilsson configuration ${{\frac{3}{2}}^{+} [402] π, {\frac{7}{2}}^{-} [503] ν}$ are suggested for 1.7-h ${}^{186}{Ir}$ .

RADIOACTIVITY ${}^{186}{Ir}$ (1.7-h isomer) [from ${}^{186}{Os} (p, n)$ ]; measured $E_{γ}$ , $I_{γ}$ , $γ - γ$ coin; deduced $log ft$ . ${}^{186}{Os}$ deduced levels, $J$ , $π$ . Enriched target, Ge(Li) detectors.

Four-body forces in nuclear matter

D. W. E. Blatt and Bruce H. J. McKellar

Phys. Rev. C 11, 2040 (1975) - Published 1 June, 1975

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The binding energy contributions to nuclear matter from four-body forces have been estimated. The four nucleon potential is written in coordinate space, and two intermediate nucleons are treated as spectators to give an effective two-body potential. Two-body correlations are included between all four nucleons and, following a coordinate transformation, two of the six dimensions for the spectator nucleons can be integrated analytically. Spin-isospin dependence is extracted and the remaining integrations are done numerically to give a one-pion-exchange-potential-like effective potential similar to the three-body force effective potentials of Loiseau, Nogami, and Ross. Binding energy calculations can then be done in the usual manner. As the number of nucleons increases the effect of exchanges of the spectator nucleons must also be considered. When this is taken into account, the over-all contribution to the energy of nuclear matter is approximately 0.1 MeV attraction.

NUCLEAR STRUCTURE Many-body forces, calculated binding $E$ of four-body force; includes correlations; effective two-body potentials.

Predictions of the masses of highly neutron-rich light nuclei

N. A. Jelley, Joseph Cerny, D. P. Stahel, and K. H. Wilcox

Phys. Rev. C 11, 2049 (1975) - Published 1 June, 1975

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A simple mass equation is derived and is shown to provide a good description of the masses of the recently measured $T_{Z} = \frac{5}{2}$ nuclei in the $s - d$ shell. A comparison is made with the method of Garvey et al. and predictions of masses and of the stability of neutron-excess light nuclei are given for both methods.

NUCLEAR STRUCTURE Derived mass equation based on shell model; compared predictions with method of Garvey et al.

Variations of nuclear potential radii in isotopic and isotonic sequences

P. C. Sood and D. C. Agrawal

Phys. Rev. C 11, 2056 (1975) - Published 1 June, 1975

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The variations of nuclear potential radii, obtained by fitting the last particle binding energies, are investigated for nuclei in the isotopic and the isotonic sequences. It is found that while the neutron (proton) potential radii increase as $A^{\frac{1}{3}}$ for nuclei in isotonic (isotopic) sequences in accordance with the universally adopted procedure in shell model and optical model studies, these radii do not show the expected behavior in the case of nuclei in isotopic (isotonic) sequences. Possible interrelationship between the variations of the potential radii and those of the nucleon separation energies and also between the potential radii and the density distribution radii in such sequences is investigated. The anomalous variations of the neutron potential radii in the isotopic sequences are found to be related with the fact that the charge distribution radii in such sequences do not increase as rapidly as $A^{\frac{1}{3}}$ . The consequences of and the possible physical explanations for such a behavior are discussed.

NUCLEAR STRUCTURE Searched potential radius to fit last particle binding energy, studied its variations in isotopic and isotonic sequences; $A = 40 - 150$ .

Radiative deexcitation of the 7.655-MeV state of ${}^{12}C$

Cary N. Davids, Richard C. Pardo, and Andrew W. Obst

Phys. Rev. C 11, 2063 (1975) - Published 1 June, 1975

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A new measurement is reported of the radiative branching ratio $\frac{Γ_{rad}}{Γ}$ for the 7.655-MeV state of ${}^{12}C$ . This quantity is needed for calculations of stellar helium burning. Coincidences between ${}^{12}C$ recoils of the proper energy and protons inelastically scattered from ${}^{12}C$ signified the radiative decay of the 7.655-MeV state. A value of (4.30 ± 0.20) × $10^{- 4}$ was obtained for the branching ratio, compared with a recent measurement of (4.20 ± 0.22) × $10^{- 4}$ and the previous best value of (2.9 ± 0.3) × $10^{- 4}$ .

NUCLEAR STRUCTURE ${}^{12}C$ , 7.655-MeV state; measured $\frac{Γ_{rad}}{Γ}$ . Stellar helium burning.

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Levels of ${}^{38}K$ : The ${}^{40}{Ca} (d, α)$ , ${}^{40}{Ca} (d, α γ)$ , and ${}^{36}{Ar} ({}^{3}{He}, p γ)$ reactions

Study of the ${}^{40}{Ar} ({}^{3}{He}, d) {}^{41}K$ reaction

Lifetime of the 563-keV level of ${}^{24}{Na}$

High-spin states of ${}^{28}{Al}$

Threshold pion production in pion - nucleus collisions: A simple estimate

Mass of ${}^{9}{Li}$

Study of the ( ${}^{6}{Li}$ , ${}^{6}{He}$ ) reactions

Transient field at nitrogen nuclei recoiling in iron and the magnetic moment of the ${}^{15}N$ first excited state

${}^{41}K ({}^{3}{He}, t)$ reaction at 25 MeV

${}^{89}Y ({}^{3}{He}, t)$ reaction at 25 MeV

( $π, d$ ) reaction for small incident pion energies

$E 2$ and $E 4$ transition moments in ${}^{172}{Yb}$ , ${}^{174}{Yb}$ , and ${}^{176}{Yb}$

Proton-induced reactions on ${}^{89}Y$

Neutron resonance spectroscopy: ${}^{177}{Hf}$

Spectroscopy of ${}^{52}{Mn}$ from the ${}^{54}{Fe} (p, {}^{3}{He})$ reaction at 40.2 MeV

Decay of the 1.7-h isomer of ${}^{186}{Ir}$

Four-body forces in nuclear matter

Predictions of the masses of highly neutron-rich light nuclei

Variations of nuclear potential radii in isotopic and isotonic sequences

Radiative deexcitation of the 7.655-MeV state of ${}^{12}C$

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