Recent Articles

High-spin states in even Hg nuclei and rotation alignment in ${}^{198}{Hg}$

C. Günther, H. Hübel, A. Kleinrahm, D. Mertin, B. Richter, W. D. Schneider, and R. Tischler

Phys. Rev. C 15, 1298 (1977) - Published 1 April, 1977

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High-spin states in even Hg isotopes populated in ( $α, xn$ ) reactions were investigated by in-beam $γ$ -ray and conversion electron spectroscopy. Several new excited states in the ground state band of ${}^{198}{Hg}$ and in the negative parity bands of ${}^{198, 200}{Hg}$ were identified. Half-lives of a number of levels in ${}^{194, 196, 198}{Hg}$ were measured. In particular we obtain $T_{\frac{1}{2}} = 1.38 (4) and 1.85 (16)$ ns for the $12^{+}$ and $10^{+}$ states in ${}^{198}{Hg}$ , respectively. Intrinsic quadrupole moments $Q_{0}$ derived from these data and the $B (E 2, 0^{+} \to 2^{+})$ agree within the limits of error. These data together with the excitation energies of the ground state band are interpreted within the rotationalignment model.

NUCLEAR REACTIONS ${}^{194, 196, 198}{Pt} (α, x n)$ , $E = 28, 31, 34, 48$ MeV; measured $E_{γ}$ , $I_{γ}$ , $γ (θ)$ , $γ (t)$ , $γ γ$ coin, $I_{c e}$ , $ce (t)$ . ${}^{194, 196, 198, 200}{Hg}$ deduced levels, $I$ , $π$ , $T_{\frac{1}{2}}$ , ICC, $Λ$ , $B (Λ)$ , Rotation-alignment model.

Isospin mixing in ${}^{111}{In}$ and the inclusion of additional terms in the mixing formalism

C. R. Lux, N. T. Porile, and S. M. Grimes

Phys. Rev. C 15, 1308 (1977) - Published 1 April, 1977

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The extent of isospin mixing in ${}^{111}{In}$ has been determined at 20.9 MeV on the basis of measured cross sections for the ( $p, p^{'}$ ), ( $p, α$ ), ( $α, p$ ) and ( $α, α^{'}$ ) reactions involving the formation of the ${}^{111}{In}$ compound nucleus. The following values were obtained for the mixing fraction and the isospin mixing matrix element: $μ = 0.62 \pm 0.14$ and $| H_{c} | = 0.013 \pm 0.004$ eV. These results are based on a reformulation of the isospin mixing theory in which additional terms are included. Previous data available for the $A \sim 50 - 70$ region are reanalyzed using this formalism and the dependence of $| H_{c} |$ on energy, mass number, and the probability of proton emission from the $T_{<} (nonanalog)$ states of the compound nucleus is determined. $| H_{c} |$ varies inversely with the first two of these quantities and directly with the third.

NUCLEAR REACTIONS ${}^{110}{Cd} (p, p^{'})$ and ( $p, α$ ) $E_{p} = 16.0$ ${}^{107}{Ag} (α, α^{'})$ MeV; ${}^{107}{Ag} (α, α^{'})$ and ( $α, p$ ), $E_{α} = 19.58$ MeV; measured differential cross sections at 30°-150°; deduced isospin mixing fraction and mixing matrix element. Theory of isospin mixing reformulated to include additional terms.

28- and 34-MeV ${}^{6}{Li}$ and ${}^{7}{Li}$ elastic scattering on nuclei with $40 \leq A \leq 91$

R. I. Cutler, M. J. Nadworny, and K. W. Kemper

Phys. Rev. C 15, 1318 (1977) - Published 1 April, 1977

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${}^{6}{Li}$ and ${}^{7}{Li}$ elastic scattering were measured at 28 and 34 MeV on ${}^{40}{Ca}$ and ${}^{48}{Ca}$ to $\frac{σ}{σ_{R}} < 10^{- 3}$ . An anomalous back angle enhancement was seen for ${}^{6}{Li}$ + ${}^{40}{Ca}$ . No set of optical model parameters tried was able to fit the back angle ${}^{6}{Li}$ + ${}^{40}{Ca}$ data. Optical model parameters which exhibited a continuous Igo ambiguity but no discrete ambiguities were obtained for the above reactions and for other Li elastic scattering on ${}^{62}{Ni}$ , ${}^{63}{Cu}$ , ${}^{64}{Zn}$ , ${}^{68}{Zn}$ , ${}^{90}{Zr}$ , and ${}^{91}{Zr}$ . For a given value of the diffuseness, all parameter sets related by the Igo ambiguity gave completely identical fits to data. The value of the diffuseness which yielded acceptable fits was limited to a narrow range. It was found that the optical model parameters are extremely sensitive to the absolute normalization of the data. An empirical formula for the optical model parameters as a function of $N$ and $Z$ of the target nucleus was obtained for both ${}^{6}{Li}$ and ${}^{7}{Li}$ elastic scattering on these targets.

NUCLEAR REACTIONS ${}^{40}{Ca}$ ( ${}^{6}{Li}$ , ${}^{6}{Li}$ ), ${}^{40}{Ca}$ ( ${}^{7}{Li}$ , ${}^{7}{Li}$ ), ${}^{48}{Ca}$ ( ${}^{6}{Li}$ , ${}^{6}{Li}$ ), ${}^{48}{Ca}$ ( ${}^{7}{Li}$ , ${}^{7}{Li}$ ); $E = 28 and 34$ MeV; measured $σ (θ)$ , $θ_{lab} = 10 - 165 °$ ; deduced optical model parameters. Deduced systematic optical model parameters Li+ ${}^{40}{Ca}$ , ${}^{48}{Ca}$ , ${}^{63}{Cu}$ , ${}^{64}{Zn}$ , ${}^{68}{Zn}$ , ${}^{90}{Zr}$ , ${}^{91}{Zr}$ .

Lifetimes of ground-band states in ${}^{192}{Pt}$ and ${}^{194}{Pt}$

Noah R. Johnson, P. P. Hubert, E. Eichler, D. G. Sarantites, J. Urbon, S. W. Yates, and Thomas Lindblad

Phys. Rev. C 15, 1325 (1977) - Published 1 April, 1977

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The lifetimes of members of the ground-state bands in ${}^{192}{Pt}$ and ${}^{194}{Pt}$ have been measured by the Doppler-shift recoil-distance technique. These states were Coulomb excited by 149 MeV ${}^{40}{Ar}$ ions and measurements were carried out in coincidence with backscattered projectiles. The half-lives of the $2^{+}$ , $4^{+}$ , and $6^{+}$ states in ${}^{192}{Pt}$ and of the $2^{+}$ and $4^{+}$ states in ${}^{194}{Pt}$ are 48.5±2.5, 4.2±0.2, 1.8±0.7, 45.0±2.4, and 3.7±0.2 ps, respectively.

NUCLEAR REACTIONS ${}^{192, 194}{Pt} ({}^{40}{Ar}^{'}, γ)$ , $E = 149$ MeV; measured lifetimes of $2^{+}$ , $4^{+}$ , and $6^{+}$ states in ${}^{192}{Pt}$ and of $2^{+}$ and $4^{+}$ states in ${}^{194}{Pt}$ ; deduced $B (E 2)$ values, compared with theory.

One-proton transfer reactions induced by ${}^{16}O$ and ${}^{12}C$ on ${}^{62}{Ni}$ target isotope

J. C. Peng, M. C. Mermaz, A. Greiner, N. Lisbona, and K. S. Low

Phys. Rev. C 15, 1331 (1977) - Published 1 April, 1977

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The ( ${}^{16}O$ , ${}^{15}N$ ) and ( ${}^{12}C$ , ${}^{11}B$ ) reactions on ${}^{62}{Ni}$ target have been investigated with 56 MeV ${}^{16}O$ and 48 MeV ${}^{12}C$ beams. Angular distributions for transitions to the first five single particle states of ${}^{63}{Cu}$ were obtained. An exact finite-range distorted-wave Born approximation analysis was performed, showing that the spectroscopic factors extracted agree fairly well with those obtained from light ion induced reactions. The role of multistep processes has also been investigated by performing exact finite-range coupled-channel Born approximation calculations which take into account the core excitation of the projectile or the target nucleus. It is found that in the case of the ${}^{62}{Ni}$ ( ${}^{12}C$ , ${}^{11}B$ ) ${}^{63}{Cu}$ reaction both the intensity and shape of the angular distributions are affected by including the multistep contributions due to projectile excitation. In particular, the behavior of the angular distributions at small angles is better described by the coupled-channel Born approximation calculations. The indirect routes involving the inelastic excitations of the ${}^{16}O$ or ${}^{62}{Ni}$ nuclei are shown to be unimportant.

NUCLEAR REACTIONS ${}^{62}{Ni}$ ( ${}^{12}C$ , ${}^{11}B$ ) $E_{{}^{12}C} = 48$ MeV; ${}^{62}{Ni}$ ( ${}^{16}O$ , ${}^{15}N$ ) $E_{{}^{16}O} = 56$ MeV $σ (θ)$ ; EFR-DWBA and EFR-CCBA analysis; deduced spectroscopic factors; enriched targets.

Classical microscopic calculations of high-energy collisions of heavy ions

A. R. Bodmer and C. N. Panos

Phys. Rev. C 15, 1342 (1977) - Published 1 April, 1977

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Nonrelativistic classical microscopic (equations of motion) calculations have been made for collisions between nuclei mostly with 50 nucleons each and for relative velocities of $0.5 c$ and $0.8 c$ (nonrelativistic laboratory energies of 117 and 300 MeV/nucleon, respectively). The trajectories of all the nucleons are calculated with two-body forces between all pairs of nucleons. The potentials are sums of attractive and repulsive Yukawa potentials of reasonable ranges and are adjusted to give reasonable binding and kinetic energies and to fit the $NN$ cross section $σ_{ν}$ appropriate for the viscosity and thus for shock phenomena; $σ_{ν}$ strongly emphasizes transverse momentum transfers. Ensemble averages are taken over (10) initial distributions and care is taken to monitor—the relativelv minor—effects of evaporation of the individual noninteracting nuclei. Central collisions corresponding to small impact parameters $b$ (less than about a nuclear radius $R$ ) are "explosive" and seem fairly well equilibrated at maximum compression and subsequently. There is some similarity to development of shocks. After an initial penetration of about a mean free path, there is rapid dissipation of the collisional translational energy with associated large internal energies and large compressions (to somewhat less than twice normal density), followed finally by an explosive expansion; the angular distributions are roughly isotropic for quite small $b$ but show some transverse peaking for very small $b$ . For small $b (≲ 0.5 R)$ and for $v = 0.5 c$ , but not for $0.8 c$ , we find large fused residues with $A \approx 60$ . Transparency and nonequilibrium effects develop rapidly with increasing $b$ and are somewhat more important for $v = 0.8 c$ than for $0.5 c$ . For $b ≳ R$ (noncentral collisions) the nuclei retain much and for $b ≳ 1.5 R$ most of their initial identity, suffering relatively little immediate mass loss with, however, quite appreciable loss of collisional translational energy for $b \approx R$ .

NUCLEAR REACTIONS HI classical nonrelativistic microscopic calculations; mostly $A_{1} = A_{2} = 50$ ; $E = 117, 300$ MeV/nucleon.

Time-dependent Hartree-Fock calculations for ${}^{16}O$ + ${}^{16}O$ and ${}^{40}{Ca}$ + ${}^{40}{Ca}$ reactions

S. E. Koonin, K. T. R. Davies, V. Maruhn-Rezwani, H. Feldmeier, S. J. Krieger, and J. W. Negele

Phys. Rev. C 15, 1359 (1977) - Published 1 April, 1977

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The time-dependent Hartree-Fock approximation is applied to ${}^{16}O$ + ${}^{16}O$ and ${}^{40}{Ca}$ + ${}^{40}{Ca}$ reactions. An effective interaction which results in a local Hartree-Fock potential is used. The full time-dependent Hartree-Fock problem is reduced to two dimensions by treating the relative orbital motion of the ions in the rotating frame approximation. The detailed dynamics of the nuclear density matrix during these reactions is discussed. The deflection function, energy loss, fragment charge distribution, and ion-ion potential have been computed for several reactions and compared with available data. The physical content and limitations of our calculations are discussed.

NUCLEAR REACTIONS ${}^{16}O ({}^{12}O, x)$ and ${}^{40}O ({}^{40}O, x)$ in time-dependent Hartree-Fock approximation. Fusion and strongly damped collisions.

Nucleus-nucleus scattering at high energies

Victor Franco and Girish K. Varma

Phys. Rev. C 15, 1375 (1977) - Published 1 April, 1977

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Nucleus-nucleus scattering is treated in the Glauber approximation. The usual optical limit result, generally thought to improve as the number of nucleons in the colliding nuclei increases, is found to be the first term of a series which diverges for large nuclei. Corrections to the optical limit are obtained which provide a means of performing realistic calculations for collisions involving light nuclei. Total cross section predictions agree well with recent measurements.

NUCLEAR REACTIONS Validity of the optical limit for heavy-ion scattering in the Glauber approximation. Effects of higher order corrections.

Kaon-nucleus inelastic scattering

S. R. Cotanch and F. Tabakin

Phys. Rev. C 15, 1379 (1977) - Published 1 April, 1977

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A theoretical investigation of kaon inelastic scattering is conducted for the specific reaction ${}^{12}C (K^{+}, K^{+'}) {}^{12}C^{*}$ ( $J^{π} = 2^{+}$ , $E_{x} = 4.43$ MeV). The analysis utilizes the Kerman-McManus-Thaler multiple scattering formalism and the distorted wave impulse approximation. The distorting parameters are uniquely determined through the empirical $K^{+}$ -nucleon scattering amplitudes. Numerical results demonstrate a clear sensitivity to choice of amplitudes. The cross sections, calculated over a wide range of energies, display a slow variation. Fermi motion effects are found to be quite important at kaon lab kinetic energies below 300 MeV. The magnitude of the $K^{+}$ -nucleus elastic $S$ matrix shows that the kaon is not strongly absorbed; however, cutoff calculations, which eliminate all internal form factor contributions, firmly establish the inelastic process is surface localized.

NUCLEAR REACTIONS Kaon inelastic scattering. KMT and DWIA. Calculated $σ (E, θ)$ for ${}^{12}C$ . Fermi motion effects. Comparison of different models. Strong absorption studies.

Pion double charge exchange on ${}^{4}{He}$

W. R. Gibbs, B. F. Gibson, A. T. Hess, and G. J. Stephenson, Jr.

Phys. Rev. C 15, 1384 (1977) - Published 1 April, 1977

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We have examined the reaction ${}^{4}{He} (π^{\pm}, π^{\mp}) 4 ({p} {n})$ in a model in which there occur two single $π - N$ charge-exchange scatterings with intermediate off-shell pion propagation between scatterings. Separable $π$ -nucleon $t$ matrices having off-shell form factors were used with fully antisymmetrized nuclear wave functions. Spin-flip of the struck nucleons was included. Both angular distributions and total cross sections were calculated and compared with available data.

NUCLEAR REACTIONS ${}^{4}{He} (π^{-}, π^{+})$ ; $E = 0 - 500$ MeV calculated $σ (E)$ ; $E = 140$ MeV calculated $σ (E)$ ; $E = 140$ MeV calculated $σ (θ = 0 °, E)$ ; $E = 485$ MeV calculated $σ (E_{f})$ .

Electromagnetic structure of the helium isotopes

J. S. McCarthy, I. Sick, and R. R. Whitney

Phys. Rev. C 15, 1396 (1977) - Published 1 April, 1977

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The elastic-electron scattering cross sections from ${}^{3}{He}$ and ${}^{4}{He}$ have been measured at incident electron energies between 170 and 750 MeV. Cross sections were separated into their longitudinal (charge) and transverse (magnetic) contributions using the Rosenbluth formula. Values of the ${}^{3}{He}$ charge form factor have been extracted to $q^{2} = 20$ ${fm}^{- 2}$ and for the ${}^{3}{He}$ magnetic form factor to $q^{2} = 16$ ${fm}^{- 2}$ . The ${}^{4}{He}$ form factor has been determined up to 6.2 ${fm}^{- 2}$ . Densities for the charge and magnetization have been deduced from phenomenological models used in a phase-shift solution of the Dirac equation. A model-independent determination of the nuclear densities has been performed in order to obtain realistic errors on the extracted distributions. After unfolding the nucleon size from the distributions the point density is shown to have a significant central depression for a radius <0.8 fm for both ${}^{3}{He}$ and ${}^{4}{He}$ . Comparison of the form factors is made with Faddeev and variational three-body calculations that use realistic two-body $NN$ interactions. The influence of off-shell effects, three-body forces, meson-exchange corrections, and short-range correlations are discussed. At present no theoretical calculation that uses input derived entirely from nucleon-nucleon scattering is able to reproduce the experimental data.

NUCLEAR REACTIONS ${}^{3, 4}{He} (e, e^{'})$ , $E = 170, 200, 250, 300, 350, 400, 450, 500, and 750$ MeV; measured $σ (E, θ)$ . Measured charge form factor ${}^{3}{He}$ to $q^{2} = 20$ ${fm}^{- 2}$ and magnetic form factor to $q^{2} = 16$ ${fm}^{- 2}$ . Measured ${}^{4}{He}$ form factor to $q^{2} = 6.2$ ${fm}^{- 2}$ . Deduced nuclear charge, magnetic and point-nucleon distributions from model-independent analysis.

Measurement of pion photoproduction at threshold on ${}^{6}{Li}$

G. Audit, A. Bloch, N. de Botton, C. Schuhl, G. Tamas, C. Tzara, J. Deutsch, D. Favart, R. Prieels, and B. Van Oystaeyen

Phys. Rev. C 15, 1415 (1977) - Published 1 April, 1977

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We remeasured with improved techniques the positive-pion photoproduction yield on ${}^{6}{Li}$ near threshold and up to 7.2 MeV above it. If the total cross section of the reaction $γ + p \to π^{+} + n$ is expressed as $σ_{p} = \frac{aq}{k}$ , our result for the reaction $γ + {}^{6}{Li} \to π^{+} + {}^{6}{He}_{g . s .}$ near threshold is $σ_{Li} = (0.098 \pm 0.004) (\frac{aq}{k}) {\frac{(\frac{12.5}{q})}{[\exp (\frac{12.5}{q}) - 1]}},$ where $q$ is the pion and $k$ the photon c.m. momenta expressed in units of MeV/c. Deviations from this expression above threshold and the contribution of $γ + {}^{6}{Li} \to π^{+} + {}^{6}{He}$ (1.8 MeV) were also observed. The full understanding of this result requires further theoretical work and complementary experiments on the $A = 6$ nuclear system.

NUCLEAR REACTIONS ${}^{6}{Li} (γ, π^{+}) {}^{6}{He}_{g . s .}$ and ${}^{6}{He}$ (1.8 MeV), $E_{π^{+}} : 0 - 7$ MeV, measured $σ$ relative to proton target.

Possible existence of abnormal nuclear density in nuclei

T. Siemiarczuk

Phys. Rev. C 15, 1425 (1977) - Published 1 April, 1977

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Neutral pion production is analyzed in $π^{-}$ Xe interactions at 9 GeV/c and, under certain assumptions, the possible existence in nuclei of collections of nucleons with abnormal density is indicated.

NUCLEAR REACTIONS $Xe (π^{-}, γ)$ ; $E = 9$ GeV; measured $E (⊖)$ of photons from $π^{0} \to 2 γ$ decay; possibility of abnormal density in nuclei.

Influence of the $Δ$ resonance on ground-state properties of nuclei

K. Holinde, R. Machleidt, Amand Faessler, and H. Müther

Phys. Rev. C 15, 1432 (1977) - Published 1 April, 1977

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Brueckner-Hartree-Fock calculations on ${}^{16}O$ are presented using a one-boson-exchange potential, which includes the $Δ (1236)$ resonance in all partial waves. The repulsive effect from the explicit treatment of the $Δ$ is considerably weaker than for the nuclear matter system. This density dependence of the repulsion leads to $NN$ interactions, which may describe the energies of finite nuclei as well as of nuclear matter.

NUCLEAR STRUCTURE Calculations for ${}^{16}O$ , one-boson-exchange potentials, influence of the $Δ$ resonance, Brueckner-Hartree-Fock approach.

Excited states in ${}^{118}{Sn}$ populated by the $β^{-}$ decay of ${}^{118}{In}^{g}$ and ${}^{118}{Sb}$

D. De Frenne, H. Thierens, E. Jacobs, P. D'hondt, A. De Clercq, K. Heyde, and A. J. Deruytter

Phys. Rev. C 15, 1440 (1977) - Published 1 April, 1977

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The ${}^{118}{In}^{g}$ activity has been obtained by chemical separation of the parent nucleus ${}^{118}{Cd}$ from a U $O_{2}$ ${(N O_{3})}_{2}$ .6 $H_{2}$ O sample, irradiated with 25- and 50-MeV bremsstrahlung. Two successive Ge(Li) $γ$ -ray supectra were measured. Several new $γ$ rays were found and the relative intensities of the known $γ$ lines are compared and discussed with respect to the existing data. Levels in ${}^{118}{Sn}$ at 0, 1229.64, 1757.8, 2043.1, 2056.5, 2326.5, 2402.5, and 3137.2 keV were found to be fed in the $β^{-}$ decay of ${}^{118}{In}^{g}$ . Based on the measured postneutron yields of the masses 111, 112, 113, 115, 117, 123, and 125 for the photofission of ${}^{238}U$ with 25- and 50-MeV bremsstrahlung, the post-neutron yield of mass 118 was obtained by interpolation, assuming a smooth behavior of the mass distribution in this region. From this the absolute intensity of the observed $γ$ lines could be determined. Intensities for all $β$ branches and corresponding $log ft$ values were calculated. The results of this study differ considerably from those known in the literature. The $β$ decay rates for ${}^{118}{In}$ and ${}^{118}{Sb}$ are compared with results of nuclear structure calculations. The systematics of $log ft$ values for the $1 g_{\frac{9}{2}} ⇄ 1 g_{\frac{7}{2}}$ Gamow-Teller $β$ decay is correlated with the filling of the $1 g_{\frac{7}{2}}$ neutron single-particle orbit for increasing $A$ .

RADIOACTIVITY ${}^{118}{In}^{g}$ [from ${}^{238}U (γ, f)$ , $E_{γ max} = 25 and 50$ MeV, chemical separation of Cd]. Measured $E_{γ}$ , $I_{γ}$ . ${}^{118}{In}^{g}$ deduced $log ft$ , ${}^{118}{Sn}$ deduced levels, $J$ , $π$ .

Mass and beta decay of ${}^{34}{Si}$

A. M. Nathan and D. E. Alburger

Phys. Rev. C 15, 1448 (1977) - Published 1 April, 1977

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${}^{34}{Si}$ has been produced via the ${}^{18}O ({}^{18}O, 2 p) {}^{34}{Si}$ reaction at 32 MeV beam energy. Identification is made from the observed $γ$ rays of energies 429.07(13) and 1607.56(50) keV, which agree with the known excitation energies of the first two excited states of ${}^{34}P$ , and from the cascade 1178.52(16)-keV transition. The three $γ$ rays decay with a common half-life of 2.77 ± 0.20 sec. Relative $γ$ -ray intensities indicate a 100% $β$ -ray branch to the 1608-keV level, and the $γ$ -ray branches of that level are determined. No information is obtained on a possible ${}^{34}{Si}$ ground-state $β$ -ray branch. From analysis of the $β$ -ray energy spectrum, a mass excess of - 19850 ± 300 keV is determined for ${}^{34}{Si}$ . Comparison with theoretical mass predictions is made.

RADIOACTIVITY ${}^{34}{Si}$ : measured $T_{\frac{1}{2}}$ , $I_{γ}$ deduced decay scheme; measured $β - γ$ coincidences; deduced $E_{0}$ ,, mass excess, $log ft$ ; compared with theory.

Decay of ${}^{128}{Cs}$

R. G. Helmer, C. W. Reich, R. J. Gehrke, R. C. Greenwood, and R. A. Anderl

Phys. Rev. C 15, 1453 (1977) - Published 1 April, 1977

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Samples of ${}^{128}{Cs}$ (3.9 min) in equilibrium with its parent ${}^{128}{(2.4 d a y)}$ have been produced by ∼800-MeV proton-induced spallation in praseodymium metal foils. Chemical purification and isotope separation have been performed to produce pure samples. Measurements of $γ$ -ray singles and $γ - γ$ coincidence spectra have been made. A total of 66 $γ$ rays between 442 and 3104 keV are assigned to the decay of ${}^{128}{Cs}$ , 57 of which have been placed in a proposed level scheme for ${}^{128}{Xe}$ involving 22 established and 3 tentative excited states. Absolute $γ$ -ray intensities have been computed based on the positron and x-ray intensities. Spin and parity assignments are proposed based on the $log ft$ values and the existence of $γ$ rays depopulating the states. The first excited $0^{+}$ state is found to occur at 1582 keV. Evidence is presented which suggests that it is of predominantly "three-phonon" character, in agreement with some theoretical predictions for transitional nuclei in this mass region.

RADIOACTIVITY ${}^{128}{Cs}$ [from Pr (spallation) ${}^{128}{Ba}$ decay]; measured $E_{γ}$ , $I_{γ}$ , $γ - γ$ ; ${}^{128}{Xe}$ deduced levels, $J$ , $π$ , $log ft$ . Isotope separation, Ge(Li) detectors.

Single-particle degrees of freedom and the generator-coordinate method

H. Müther, K. Goeke, K. Allaart, and Amand Faessler

Phys. Rev. C 15, 1467 (1977) - Published 1 April, 1977

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The generator-coordinate method which is usually used to describe collective degrees of freedom is extended to include two quasiparticle excitations and the coupling between these two different modes. As generating wave functions angular momentum and particle number projected Hartree-Fock-Bogoliubov states and quasiparticle excitations built on them are used. The Hartree-Fock-Bogoliubov functions are constrained to a given quadrupole moment, which serves as the generator coordinate. This method is applied to the $pf$ - shell nuclei ${}^{46, 50}{Ti}$ , ${}^{52}{Cr}$ , and ${}^{54}{Fe}$ .

NUCLEAR STRUCTURE Generator coordinate method; Hartree-Fock-Bogoliubov approach; angular momentum projection; particle number projection; two-quasiparticle configurations; nuclear structure calculation in Ti, Cr, and Fe.

Properties of Griffin-Hill-Wheeler spaces

A. F. R. de Toledo Piza, E. J. V. de Passos, D. Galetti, M. C. Nemes, and M. M. Watanabe

Phys. Rev. C 15, 1477 (1977) - Published 1 April, 1977

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We discuss a method for constructing an explicit orthonormal representation for the collective subspace associated with the generator coordinate method, assuming that the overlap $〈 α | α^{'} 〉$ is a Hilbert-Schmidt kernel in the space of weight functions. We show that the equivalence between the diagonalization of the many-body Hamiltonian in the collective subspace and the solution of the Griffin-Hill-Wheeler equation is a dynamical question which cannot be answered by kinematical considerations alone. The treatment gives a simple picture of well known misbehaviors of the generator coordinate weight functions. An application is made to the Lipkin model.

NUCLEAR STRUCTURE Properties of generator coordinate representations. Application to a solvable model.

Central and noncentral components of the effective $sd$ -shell interaction

K. Klingenbeck, W. Knüpfer, M. G. Huber, and P. W. M. Glaudemans

Phys. Rev. C 15, 1483 (1977) - Published 1 April, 1977

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The contributions of central as well as noncentral two-body interactions to the matrix elements of various effective interactions for the $sd$ shell are studied in an SU(3) two-particle basis. The results show that their central parts agree rather well and exhibit an approximate SU(3) symmetry. However, large differences are found between the noncentral parts of microscopic and phenomenological interactions, respectively. The influence of noncentral components of the matrix elements of Glaudemans et al. on experimental data is investigated for the case of ${}^{28}{Si}$ , with the result that the $LS$ component is very important to reproduce the correct ground state binding energy. Some effects introduced by higher order two-body interactions and many-body interactions are discussed.

NUCLEAR STRUCTURE Tensor components of effective ( $sd$ ) interaction, SU(3) two-particle basis. Application to ${}^{28}{Si}$ .

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High-spin states in even Hg nuclei and rotation alignment in ${}^{198}{Hg}$

Isospin mixing in ${}^{111}{In}$ and the inclusion of additional terms in the mixing formalism

28- and 34-MeV ${}^{6}{Li}$ and ${}^{7}{Li}$ elastic scattering on nuclei with $40 \leq A \leq 91$

Lifetimes of ground-band states in ${}^{192}{Pt}$ and ${}^{194}{Pt}$

One-proton transfer reactions induced by ${}^{16}O$ and ${}^{12}C$ on ${}^{62}{Ni}$ target isotope

Classical microscopic calculations of high-energy collisions of heavy ions

Time-dependent Hartree-Fock calculations for ${}^{16}O$ + ${}^{16}O$ and ${}^{40}{Ca}$ + ${}^{40}{Ca}$ reactions

Nucleus-nucleus scattering at high energies

Kaon-nucleus inelastic scattering

Pion double charge exchange on ${}^{4}{He}$

Electromagnetic structure of the helium isotopes

Measurement of pion photoproduction at threshold on ${}^{6}{Li}$

Possible existence of abnormal nuclear density in nuclei

Influence of the $Δ$ resonance on ground-state properties of nuclei

Excited states in ${}^{118}{Sn}$ populated by the $β^{-}$ decay of ${}^{118}{In}^{g}$ and ${}^{118}{Sb}$

Mass and beta decay of ${}^{34}{Si}$

Decay of ${}^{128}{Cs}$

Single-particle degrees of freedom and the generator-coordinate method

Properties of Griffin-Hill-Wheeler spaces

Central and noncentral components of the effective $sd$ -shell interaction

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