In the Brookhaven National Laboratory 20.8-GeV/c negative hyperon beam, we have measured the branching ratios $\frac{({\Sigma }^{-}\to \Lambda e^{-}\nu )}{({\Sigma }^{-}\to n{\pi }^{-})}$ and $\frac{({\Xi }^{-}\to \Lambda e^{-}\nu )}{({\Xi }^{-}\to \Lambda {\pi }^{-})}$. From a total of ${10}^6$ ${\Xi }^{-}$ topology triggers, of which 7.5 × ${10}^5$ have an electron Čerenkov counter in coincidence, we find 127 ${\Sigma }^{-}\to \Lambda e^{-}\nu$ candidates and 15 ${\Xi }^{-}\to \Lambda e^{-}\nu$ candidatates including about 4% background for ${\Sigma }^{-}\to \Lambda e^{-}\nu$ and about 30% background for ${\Xi }^{-}\to \Lambda e^{-}\nu$. We measure the branching ratios to be (0.60 ± 0.06) × ${10}^{-4\mathrm{}}$ and (0.31 ± 0.11) × ${10}^{-3\mathrm{}}$, respectively.

An experiment is described which shows that a 3-μA beam of polarized ${\mathrm{H}}^{-}$ of ${\mathrm{D}}^{-}$ ions can be produced by bombarding polarized thermal hydrogen atoms with a beam of 40-keV cesium atoms. The observed beam polarization is consistent with the assumption that there is no depolarization in the collision ${\left({\mathrm{H}}^0\right)}_{\mathrm{pol}}$ + ${\mathrm{Cs}}^0$ → ${\left({\mathrm{H}}^{-}\right)}_{\mathrm{pol}}$ + ${\mathrm{Cs}}^{+}$. The emittance of the beam is sufficiently small for good transmission through tandem accelerators.

Simple shell-model calculations account for the remarkable similarity in excitation energies and ($t, p$) strengths of predominantly ${\mathrm{}\left(\mathrm{sd}\right)\mathrm{}}^2$ states in ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{C}$.

The binding energy of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is calculated within the framework of the Yakubovsky equations for the Reid soft-core potential. Use is made of separable expansions of the subamplitudes. With neglect of the Coulomb effect and the non-$s$-wave parts of the two-nucleon $t$ matrix, the binding is found to be 19.5 MeV. With use of the solutions of the integral equations the elastic charge form factor is calculated. In addition to the underbinding of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ it is found that the secondary maximum in the form factor is much too low as compared to experiment.

We have measured the ionization loss of electrons with Lorentz factors $\gamma =2.91\mathrm{}$ and $1.6\times {10}^4<~\gamma <~{10}^5$ passing through a (100.71 ± 0.15)-μm silicon detector. Our results are in agreement with accepted theory for $\gamma =2.91\mathrm{}$ and $\gamma =1.6\mathrm{}\times {10}^4$; however, for $\gamma >~3\times {10}^4$ our results are systematically (7 ± 2)% below the theoretical value. We suggest an explanation in terms of the finite detector thickness and a relativistic effect.

First, second, and third moments of gamma-ray multiplicity distributions from deeply inelastic collisions have been measured for the system ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ on ${}_{}{}^{144}{}_{}{}^{}\mathrm{Sm}$ at 490-MeV Kr energy. The average gamma-ray multiplicities are ≈ 21, independent of reaction angle and fragment charge. The multiplicity distributions are broad, with standard deviations of $v\approx 10$, and they have a negative skewness.

We report the electron-induced fission of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ into two ground-state ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ nuclei following monopole excitation at energies between 20 and 22 MeV. The observed cross section exhausts at least (8±2)% of the linear energy-weighted monopole sum rule $S\left(E0\mathrm{}\right)\mathrm{}$ and may form a part of the giant monopole resonance. In addition, we have observed a peak in the ${\theta }_{{}_{}{}^{12}{}_{}{}^{}\mathrm{C}}=45\mathrm{}°$ excitation function between 22.0 and 23.5 MeV with a width (full width at half-maximum) < 1 MeV and a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ angular distribution, ${sin}^2\left(2\mathrm{}{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\right)$, indicating $J^{\pi }=2^{+}$.

The yield curves of high-energy capture $\gamma$ rays from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, {\gamma }_0)$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, {\gamma }_1)$ were measured at ${\theta }_{\mathrm{lab}}=45\mathrm{}°$ from $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=5.0\mathrm{} \mathrm{to} 11.0$ MeV. A $J^{\pi }=2^{+}$ resonance, with a width (full width at half-maximum) of 261±74 keV and a peak cross section at 45° of 44.3±4.5 nb/sr, was observed in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, {\gamma }_0)$ at (21.98±0.03) MeV excitation in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$. Several other resonant features were also observed in the $\gamma$-ray yields.

The first elastic-scattering analyzing-power ($A_y$) data at 0.8 GeV are presented and discussed. Angular distributions of $A_y$ over the range 2° to 20° (30° for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$) have been obtained for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ using the high-resolution spectrometer at the Clinton P. Anderson Meson Physics Facility. The analyzing powers oscillate sharply over positive values in qualitiative agreement with expectations.

Ion yields of ${\mathrm{He}}^{+}$ scattered from atomic and solid Pb in the energy range from 200 to 2000 eV into a large scattering angle are reported. The beam results show an oscillatory structure of the ion yield as function of the energy which is comparable to the same effects observed for a solid target. Thus the atomic nature of the quasiresonant charge exchange is confirmed. The data also give evidence for solid-state effects influencing the oscillations of the ion yield.

Angular correlations have been measured between electrons exciting the $2p$ state of hydrogen and the Lyman-$\alpha$ decay photons at incident energies of 70 and 100 eV and electron scattering angles of 5°, 10°, and 15°. The information obtained on the scattering amplitudes to the magnetic substates is compared with recent calculations, none of which are in good agreement with all of the data.

Hamiltonian perturbation theory based on recent Lie transform techniques is applied to the Hamiltonian of a single particle in nonuniform Vlasov plasma. A simple relation is derived between the field-plasma interaction energy and the transformed single-particle Hamiltonian. This relation implies as special cases a general formula for ponderomotive force in terms of the linear Vlasov susceptibility, and a symmetric Poisson-bracket formula for the general three-mode coupling coefficient.

Because of the similarity of their order parameters, there are close analogies between defects of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ and cholesteric liquid crystals. In particular, boojums, originally predicted for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$, should exist as well in cholesterics. Certain textures experimentally observed and reported in the literature are identified as boojums. A topological analysis is given, and the effects of boojums on dynamical properties of cholesterics are discussed.

The transition hcp ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ to fcc ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ shows temperature hysteresis. The difference between the transition temperature in heating and in cooling is 25 mK near the triple point, and it increases with increasing pressure. The transition is believed to be of martensitic type. Latent heat measurements indicate that above 16 K only partial transformation occurs.

A first-order phase change is observed in a dense monolayer of xenon adsorbed on the cleavage face of nickel chloride. This is the first observation of such a transition for rare gases on a surface other than the basal plane of graphite. We conjecture that it is a solid-solid transition rather than a solid-liquid one.

We report transverse and longitudinal NMR experiments on superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ confined within 2-μm-diam tubes at temperatures down to 1 mK. The behavior of the transverse resonance line provides evidence for a slow transition between two textures in the tubes; the shifts are smaller than in bulk for both textures. A search for longitudinal resonance was unsuccessful, and no transition to the $B$ phase was observed.

From a measurement and analysis of the extended fine structure on the Ge $K$-shell absorption cross section, we determine that the metalloid (Ge) nearest-neighbor environments in arc-quenched glassy ${\mathrm{Pd}}_{78}$${\mathrm{Ge}}_{22}$ and in sputtered amorphous ${\mathrm{Pd}}_{80}$${\mathrm{Ge}}_{20}$ are essentially identical. Conclusive evidence is presented for the occurrence of chemical ordering. The glass structure is shown to be substantially modified by the presence of the metalloids, bringing into question the applicability of models based upon a structure determined by the metal atoms alone.

The spontaneous magnetization, the zero-field susceptibility, and the isothermal critical magnetization along the ferromagnetic axis of Tb${\mathrm{F}}_3$ in the critical region have been measured and can best be described by mean-field laws with logarithmic corrections as predicted by recent renormalization-group calculations for uniaxial, dipolar-coupled ferromagnets. Furthermore, the three critical amplitudes satisfy the predicted amplitude relation between them.

The EPR of ${\mathrm{Gd}}^{3+}$ impurities in the interconfiguration-fluctuation (ICF) host Ce${\mathrm{Pd}}_3$ is reported. The observed linewidth is consistent with an intrinsic relaxation rate proportional to $T$, where the proportionality constant is 3 times smaller than in the isostructural non-ICF host Y${\mathrm{Pd}}_3$. Although contrary to what is suggested by simple fluctuation concepts, such an effect of ICF on the EPR linewidth is actually to be expected theoretically.

The dispersion of the volume plasmon of silicon at 16.7 eV has been measured with 50-keV electrons in the directions $〈100〉$ and $〈111〉$ up to the critical wave vector $q_c\simeq 1.1$ ${\mathrm{\AA }}^{-1\mathrm{}}$. It shows a strong anisotropy. Along the $〈100〉$ direction the $q$ dependence could be measured up to large $q$ vectors of ∼2.4 ${\mathrm{\AA }}^{-1\mathrm{}}$. At $q\gtrsim q_c$ the slope of the dispersion curve decreases strongly in a manner similar to what has been found earlier for Al and Be.