The value of the electron capture branching ratio of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ to the 478 keV state in ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ has been measured using sources of determinable intensity fabricated by capturing in silicon surface barrier detectors ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ recoils from the ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}(\mathrm{p}, \alpha ){}_{}{}^7{}_{}{}^{}\mathrm{Be}$ reaction at $E_{\mathrm{p}}=1.5\mathrm{} \mathrm{MeV}\mathrm{and} 4.5 \mathrm{MeV}$ Results from independent measurements utilizing detectors implanted in a scattering chamber and in the focal plane of a magnetic spectrograph are in good agreement. An absolute determination of the rate at which the 478 keV gamma rays were emitted from each source yielded a weighted average value of 10.6±0.5% for the branching ratio. This result is in agreement with the previously accepted value of 10.37±0.12% and does not support the recent suggestion that the branching ratio is appreciably larger.

RADIOACTIVITY ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}(\mathrm{p}, \alpha ){}_{}{}^7{}_{}{}^{}\mathrm{Be}$, $E=1.5, 4.5$ MeV; enriched target; measured $I_{{}_{}{}^7{}_{}{}^{}\mathrm{Be}}$; silicon surface barrier detector; measured $E_{\gamma }$, $I_{\gamma }$; Ge(Li) detector; deduced branching ratio of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ to 478 keV state in ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$.

The branching ratio for ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ electron-capture decay to the first excited state in ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ has been measured by implanting a 20-MeV ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ beam into a silicon detector telescope and counting the subsequent $\gamma$ decays with well calibrated Ge(Li) detectors. A branching ratio of 10.7±0.2% was obtained. This value is in agreement with past measurements but does not agree with a recently suggested higher value. Sources of uncertainties and implications for nuclear physics and astrophysics are discussed.

RADIOACTIVITY ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$; measured the EC branching ratio to the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ first excited state.

The branching ratio for the electron-capture decay of ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ to the 478 keV state in ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ has been measured. ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ nuclei recoiling near zero degrees from the ${}_{}{}^1{}_{}{}^{}\mathrm{H}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$)n reaction were counted by and implanted into a Si detector placed in the focal plane of an Enge split-pole spectrograph. After determining the total number of implanted ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ nuclei from the pulse height spectrum, the absolute number of 478 keV $\gamma$ rays was measured with a Ge(Li) detector. The resulting branching ratio of 10.61±0.23% agrees well with previous measurements.

RADIOACTIVITY ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$; measured $I_{\gamma }$, deduced branching ratio to 478-keV first-excited state of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$.

Several shell model configurations entitled to describe a spin-isospin phase in nuclei are analyzed at different nuclear densities and deformations in the region $A=12-36\mathrm{}$. Shell effects are found to be dominant. As a result, the spin-isospin alignment (${\sigma }_3{\tau }_3=+1\mathrm{}$ or ${\sigma }_3{\tau }_3=-1\mathrm{}$) is most favored in nuclei around $A=28\mathrm{}$ because of their distinctive shell model structure. Moreover, in a given nucleus an energy gain over the normal and other possible phases can be obtained at reasonably low densities, if a fraction rather than the totality of nucleons have the same spin-isospin alignment. The analysis of the results strongly suggests that the ordered phase should be described by a correlated shell model state composed of a suitable number of these partially ordered configurations. The relevance of the results to possible collective properties of properly chosen nuclei at ordinary density is pointed out.

NUCLEAR STRUCTURE Spin-isospin phases in nuclei. Shell model. Totally ordered, partially ordered configurations.

The effect of finite boson number in the interacting boson approximation is one of its most distinguishing features. These effects are investigated in terms of the deviations of $\gamma \to g$ band $E2\mathrm{}$ transitions from the rotational (Alaga) values which provide one of the most crucial tests of collective models of deformed nuclei. It is shown that the empirical systematics of these deviations displays a strong mass dependence, that the interacting boson approximation successfully reproduces these systematic trends, and does so primarily by virtue of the variations in boson number and not because of parameter variations. Moreover, the origin of the $N$ dependence lies in the characteristic way in which the SU(3) symmetry is broken in calculations for realistic deformed nuclei and involves, in an essential way, the $N$ dependence of the SU(3) $\gamma \to \beta$ transitions.

NUCLEAR STRUCTURE Interacting boson model, finite boson number effects, relation to geometric models.

Two inequivalent quantum mechanical versions of the liquid drop model can be obtained, depending on whether the classical volume conservation condition is imposed to first or second order. These two models have dynamical groups IU(5) and U(6), respectively. The two models are related to each other through standard group contraction and group expansion procedures.

NUCLEAR STRUCTURE Liquid drop model, dynamical symmetry, first and second order volume conservation, inhomogeneous unitary group, contraction and expansion of groups.

Total binding energies for nuclei with $14\le A\le 18$ are obtained from a realistic effective no-core Hamiltonian, $H_{\mathrm{eff}}$, using moment methods. The lowest few moments of $H_{\mathrm{eff}}$ are evaluated in an oscillator model space of four major shells. These moments are then used to determine a number of continuous and discrete density of states functions, each of which yields an estimate for the $H_{\mathrm{eff}}$ ground state energy. The adjustable discrete density of states functions which we introduce are based upon realistic single-particle Hamiltonians. With a reasonable selection of moment method ingredients we obtain good agreement between theory and experiment for relative binding energies within each $A$ chain. The most stable isobar is correctly predicted in all cases and Coulomb energy differences are in close agreement with experiment. Thus, the valley of $\beta$ stability is well reproduced in this approach with a simple overall shift in absolute binding energies for each $A$ chain.

NUCLEAR STRUCTURE Binding energies from moment methods; spectral properties of realistic effective no-core Hamiltonian; approximate density of states function based on realistic single-particle Hamiltonians.

A study of $\gamma$-ray data produced by neutron inelastic scattering from a lead sample enriched in the isotope ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ has resulted in placements of 106 $\gamma$ rays as transitions among 88 known or postulated levels of the ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ level structure.

NUCLEAR REACTIONS ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}(\mathrm{n}, {\mathrm{n}}^{\prime }\gamma )$; $E_{\mathrm{n}}<~8$ MeV; radiogenic sample; measured $E_{\gamma }$, relative $I_{\gamma }$; deduced ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ levels, transitions.

The average energy-to-charge state ratios of evaporation residues from fusion of Ni+Sn are measured using an electrostatic deflector combined with $\Delta E-E$ particle identification. The deduced average atomic charge states are 5 to 13 units higher than the equilibrium values expected from stripping in the target, suggesting that nuclear decays outside the target foil play an important role. The importance of internal conversion in determining these anomalously high charge states is discussed.

NUCLEAR REACTIONS ${}_{}{}^{114,124}{}_{}{}^{}\mathrm{Sn}$ (${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, fusion); $E_{\mathrm{lab}}=281\mathrm{}$ MeV; measured $〈\frac{E}{q}〉$; evaporation residues; deduced average atomic charge states; discussed role of internal conversion, implications for superheavy nuclei searches.

Coulomb excitation studies have been performed on an enriched ${}_{}{}^{189}{}_{}{}^{}\mathrm{Os}$ target with a 56 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ beam. Gamma rays were measured in coincidence with the backscattered ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions. Rotational bands built on ${\frac{3}{2}}^{-}\mathrm{}\left[512\right]\mathrm{}$, ${\mathrm{½}}^{-}$ [510] up to spin $\frac{11}{2}$ have been identified.

NUCLEAR REACTIONS ${}_{}{}^{189}{}_{}{}^{}\mathrm{Os}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$′); $E=56\mathrm{}$ MeV, enriched target measured $E_{\gamma }$, $I_{\gamma }$.

The "counting of maxima" method of Brink and Stephen, conventionally used for the extraction of the correlation width of statistical (compound nucleus) reactions, is generalized to include precompound processes as well. It is found that this method supplies an important independent check of the results obtained from autocorrelation studies. An application is made to the reaction ${}_{}{}^{25}{}_{}{}^{}\mathrm{Mg}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$,p).

NUCLEAR REACTIONS Statistical multistep compound processes discussed.

The parametrizations developed by Spuller and Measday for the energy dependence of the total cross section for $\pi \mathrm{d}\to \mathrm{pp}$, which have been used to normalize some $\pi \mathrm{d}\to \mathrm{pp}$ angular distributions, are reviewed in light of high accuracy data taken since 1975. Slight modifications of the parameters of the earlier analysis yield significant improvement in the agreement with the newer data. A simpler parametrization which fits the data equally well is suggested for absolute normalizations of relative angular distributions for the process.

NUCLEAR REACTIONS $\mathrm{d}({\pi }^{+}, \mathrm{p})\mathrm{p}$, $T_{\pi }<330\mathrm{}$ MeV; parametrization of $\sigma \mathrm{}\left(E\right)\mathrm{}$ using phenomenological formulas; discussion of previous work; comparison with data; simple formula suggested for absolute normalization of measured relative $\frac{d\sigma }{d\Omega }$.

We describe the giant resonances as simple scaling solutions of a linearized Vlasov equation obtained from a time-dependent Hartree-Fock theory in phase space. For ellipsoidal deformed nuclei we get a splitting of the isoscalar giant quadrupole resonance proportional to the ground state charge quadrupole moment. The lower energy state ($\hslash {\omega }_{\parallel }$ for prolate nuclei, $\hslash {\omega }_{\perp }$ for oblate) always gets the larger electromagnetic strength.

NUCLEAR STRUCTURE Giant resonances. Nuclear deformation. Nuclear fluid dynamics.

Isospin conservation in nucleon-nucleon scattering leads to an extension of the optical theorem to backward angles. The total neutron-proton and proton-proton cross sections are related to the imaginary parts of the neutron-proton amplitudes at backward angles. We suggest to incorporate the above relations in the phase shift analysis, especially above 600 MeV lab energy were dibaryons are suspected to exist.

NUCLEAR REACTIONS Nucleon-nucleon scattering, isospin conservation.

The modified Tamm-Dancoff approximation is applied to odd Ni isotopes after incorporating the Lipkin-Nogami procedure to improve the nonconservation of number of particles. The numerical calculations are performed employing the Kuo-Brown effective interaction. The Lipkin-Nogami procedure is found to give a general improvement in the agreement with the data.

NUCLEAR STRUCTURE MTDA method using Lipkin-Nogami approach, odd Ni isotopes. Kuo-Brown interaction.

The strong absorption limit of the Blankenbecler-Goldberger amplitude for hadron-nucleus elastic scattering is studied by calculating the total cross section using the optical theorem, and comparing the results to values obtained in the Glauber model. It is shown that in spite of many defects, the Blankenbecler-Goldberger amplitude yields results not too far from those of Glauber. This is due to the fact that most of the elastic scattering is concentrated in the nuclear surface, and that the two multiple scattering expansions agree in low density regions.

NUCLEAR REACTIONS Properties of high-energy amplitudes for hadron-nucleus scattering.

The nuclear form factor arising from the Fermi density function is shown to be completely determined by the pole of the density function closest to the real axis.

NUCLEAR REACTIONS Nuclear form factor for Fermi shape, dependence on poles of nuclear density.

The low-lying level structure of ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$ has been examined by the (n, ${\mathrm{n}}^{\prime }\gamma$) reaction and all known levels with $J<\mathrm{}7\mathrm{}$ and $E_x<~2.0$ MeV are observed. The discovery of a level at 1893 keV calls for a reexamination of the completeness of the level scheme assumed previously for this nucleus. No new low-lying candidates for two-phonon $\gamma$ vibrations are observed.

NUCLEAR REACTIONS ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}(\mathrm{n}, {\mathrm{n}}^{\prime }\gamma )$, $E_{\mathrm{n}}=1.0-3.5\mathrm{}$ MeV; measured $E_{\gamma }$, $I_{\gamma }$, $\sigma (E, E_{\gamma }, {\theta }_{\gamma })$. Searched for two-phonon states.

Recently measured neutron-proton angular correlations in the deuteron-induced breakup reactions at 56 MeV incident energy have been analyzed in terms of the post form distorted-wave Born approximation theory of breakup reactions. Comparison of the present results is made with those of the prior form distorted-wave Born approximation calculations. It is found that the results of the post form distorted-wave Born approximation calculations are in better agreement with the experimental data than the prior form distorted-wave Born approximation results.

NUCLEAR REACTIONS $A(\mathrm{d},\mathrm{p}\mathrm{n})$ elastic breakup reactions at $E_{\mathrm{d}}=56\mathrm{}$ MeV; $A={}_{}{}^{12}{}_{}{}^{}\mathrm{C}, {}_{}{}^{51}{}_{}{}^{}\mathrm{V}, {}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}$; calculated $\frac{d^2\sigma }{d{\Omega }_{\mathrm{p}}d{\Omega }_{\mathrm{n}}}$ and $\frac{d^3\sigma }{d{\Omega }_{\mathrm{p}}d{\Omega }_{\mathrm{n}}d{E}_{\mathrm{p}}}$; post form DWBA theory of breakup reactions comparison with prior form DWBA theory.

The results of a calculation using a newly developed statistical emission formalism are compared with the recently published data of Finn et al. for nuclear fragment yields from high energy proton-nucleus interactions on ${}_{}{}^{132}{}_{}{}^{}\mathrm{Xe}$. Good agreement is noted.

NUCLEAR REACTIONS Statistical emission, heavy mass fragments from high energy reactions.