Differential cross sections were measured for inelastic scattering of 164-MeV ${\pi }^{+}$ and ${\pi }^{-}$ from ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$. Large cross-section ratios, $R=\frac{\sigma \left({\pi }^{+}\right)}{\sigma \left({\pi }^{-}\right)}$ (or $R^{-1\mathrm{}}$), were observed, two being significantly larger than the free $\pi$-nucleon value. Lower limits are $R>\mathrm{}26\mathrm{}$, $R^{-1\mathrm{}}>17\mathrm{}$, and $R>\mathrm{}11\mathrm{}$ for states at 8.32 MeV ($2^{+}$), 11.67 MeV ($4^{-}$), and 17.26 MeV ($4^{-}$), respectively. These values are interpreted as being due to strong cancellations of the neutron and proton components of the transition amplitudes.

A sensitive test of hadronic charge symmetry has been made by comparing differential cross sections for ${\pi }^{+}$ and ${\pi }^{-}$ elastic scattering from deuterium at 143 MeV. Coulomb effects were calculated with the three-body Faddeev formalism. After corrections for Coulomb effects the cross-section ratio indicates that charge symmetry is valid to within (0.4±0.5)%.

The u(3)-boson model encompasses both the Elliott su(3) and Bohr-Mottelson collective models. The microscopic foundation of the u(3)-boson model is achieved by showing that it is the liquid (i.e., many nucleon) limit of the microscopic collective sp(3,$R$) theory. For ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ we construct microscopic vibrational states in the sp(3,$R$) theory which compare remarkably well with the simpler u(3)-boson prediction.

Results of nuclear-matter calculations are presented for several nucleon-nucleon potentials that fit scattering data and deuteron properties. The results suggest that two-body potentials cannot account quantitatively for nuclear saturation.

$\Lambda$'s produced in central collisions of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$+KC1 at 1.8-GeV/u incident energy were detected in a streamer chamber by their charged-particle decay. For central collisions with impact parameters $b<\mathrm{}2.4\mathrm{}$ fm the $\Lambda$ production cross section is 7.6±2.2 mb. A calculation in which $\Lambda$ production occurs in the early stage of the collision qualitatively reproduces the results but underestimates the transverse momenta. An average $\Lambda$ polarization of -0.10±0.05 is observed.

The radiative properties of an atom in a cavity differ fundamentally from the atom's radiative properties in free space. Spontaneous emission is inhibited if the cavity has characteristic dimensions which are small compared to the radiation wavelength, and enhanced if the cavity is resonant. The cavity causes slight shifts in the energies of the atom, analogous to radiative shifts. Experiments are proposed for observing these effects.

Theoretical and experimental studies of nuclear polarization induced by single-mode—laser optical pumping are reported. The nuclear polarization is shown to depend on the product of laser intensity and buffer-gas pressure. In ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ it approaches one at modest laser intensities (∼100 mW/${\mathrm{cm}}^2$) for pressures as small as a few hundred millitorr.

We report the first observation of laser-assisted collisions in molecules. Cross sections for such intermolecular processes involving high-energy ($E\sim 11$ eV) Rydberg states in carbon monoxide are shown to be larger than ${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ at the laser intensities approaching ${10}^{10}$ W/${\mathrm{cm}}^2$. Our experiments clearly illustrate the care necessary in interpreting multiphoton spectra taken at high laser powers.

We present the results of measurements of the vertical and horizontal temperature gradients in a Rayleigh-Benard cell. By an appropriate preparation of the initial state, the system can be brought into a single-frequency oscillatory regime. Further stepwise increase in the imposed temperature gradient makes the system go through a reproducible sequence of period-doubling bifurcations up to $\frac{f_1}{16}$. The Feigenbaum $\delta$ and $\mu$ universal numbers are determined.

A simple self-consistent limitation of the anisotropic portion of the local electron distribution function results in an order-of-magnitude reduction from the Spitzer-Härm thermal heat flux in steep temperature gradients, in agreement with recent Fokker-Planck simulations. A new upper bound derived for the local heat flux, substantially lower than that given by a "free-streaming" limit, accounts for most of the "inhibition" previously required in the interpretation of many experiments with high-power-laser-produced plasma.

A formalism for determining the behavior of vortex filaments in the presence of pinning sites is presented. As an initial application, the properties of a single quantized vortex terminating on a geometrically simple pinning site and subject to pure superflow are investigated. It is found that there exists a critical velocity above which the vortex decouples from the pinning site by a nonlinear, discontinuous process arising from its interaction with the nearby boundaries. No evidence of a vortex-mill mechanism is observed.

We report the microwave conductivity of a single crystal of the superionic conductor hollandite (${\mathrm{K}}_{1.54}$${\mathrm{Mg}}_{0.77}$${\mathrm{Ti}}_{7.23}$${\mathrm{O}}_{16}$). The charge carriers are potassium ions which propagate along channels. Transport is determined by thermally activated hopping of the potassium collective coordinate over an effective potential barrier. The conductivity effective barrier height agrees with a model which accounts for the structural parameters of hollandite. This represents the first detailed agreement between transport and structural data for a superionic conductor.

Large corrections to scaling have been discovered in the susceptibility $\chi$ and in the order parameter $m$ of the binary mixture triethylamine-water, allowing accurate determinations of the universal exponent $\Delta =0.52\mathrm{}\pm 0.03$ and of the correction amplitudes ${a_{\chi }}^{+}$ and ${a_m}^{-}$. Together with our previous determination of the specific-heat correction amplitude ${a_c}^{+}$, this allows the calculation of three different universal ratios, in particular $\frac{{a_c}^{+}}{{a_{\chi }}^{+}}=7.9\mathrm{}\pm 1.2$, which agrees well with the theoretical prediction 8.5±0.9 obtained by field theories.

The range of metals and temperatures for which positive muon diffusion is measurable can be expanded greatly by doping nonmagnetic metals with paramagnetic ions. In these systems, the diffusivity determines the time needed for the ${\mu }^{+}$ to reach the sites of strong depolarization near the paramagnetic ions and hence the depolarization rate of the muon spin rotation signal. For $\mathrm{Au}\mathrm{Gd}$ and $\mathrm{Au}\mathrm{Er}$ we have measured diffusion-induced depolarization for temperatures between 85 and 230 K, and have determined that there is an important short-range component in the muon-ion interaction.

The probability distributions for switching out of the superconducting state of low-cur-rent-density 1-μm Nb Josephson junctions with capacitance ≈ 0.1 pF have been measured as a function of temperature $T$ down to 3 mK. Below 100 mK the distribution widths become independent of $T$. The results are in excellent agreement with predictions for the quantum tunneling of the (macroscopic) junction phase that include the reduction of tunneling rates due to dissipation.

We have obtained evidence from ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ NMR measurements that the C${\mathrm{N}}^{-}$ ion in the elastically ordered phase of KCN is misoriented slightly with respect to the orthorhombic $b$ axis. This misorientation varies randomly over the lattice, averaging to zero on a macroscopic scale. The misorientations are manifested through small-angle C${\mathrm{N}}^{-}$ reorientations which contribute to the spin-lattice relaxation time $T_1$ of the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ nuclei, via dipolar interactions and chemical shift anisotropy.

Measurements have been made on the Doppler broadening of the 511-keV photons resulting from positron annihilation in a single cadmium crystal over the temperature range 4-590 K. They show that the temperature dependence in the prevacancy region (150-350 K) is markedly different in the cases of emission in the [0001] and $\left[10\mathrm{}\overline{1}0\right]$ directions.

We calculate the spin and charge dynamical susceptibilities of an intermediate-valence system fluctuating between two magnetic configurations. Our results can explain the most important features of the neutron-scattering spectra of TmSe. We show that the energy of the inelastic peak found experimentally is connected with the energy of charge fluctuations.

An analysis of the observed values of the lattice constants of the crystalline solutions Ce${\mathrm{Ir}}_2$-Ce${\mathrm{Pt}}_2$ and other Friauf-Laves intermetallic compounds leads to the conclusion that at 14 at.% Ce${\mathrm{Pt}}_2$ in Ce${\mathrm{Ir}}_2$ the platinum atom has transferred one electron to cerium and forms nine covalent bonds in pivoting resonance, without having a metallic orbital, whereas in La${\mathrm{Pt}}_2$ and Ce${\mathrm{Pt}}_2$ it has 0.72 metallic orbital, an unshared electron pair, and covalence 7.28. The choice of valence states $3^{+}$ and $4^{+}$ of cerium in different compounds is also discussed.

We present a semisimple grand unifying $\mathrm{SO}{\mathrm{}\left(10\right)\mathrm{}}_V\otimes \mathrm{SO}{\mathrm{}\left(10\right)\mathrm{}}_H$ gauge theory in which $\mathrm{SO}{\mathrm{}\left(10\right)\mathrm{}}_H$ is an extended hypercolor group. This extended hypercolor group contains both an SO(6) hypercolor subgroup and an SO(4) generation-counting subgroup. The model gives rise to both radiatively induced mass and mass mixing terms for the usual fermions. Under reasonable assumptions, the value ${tan}^2{\theta }_{\mathrm{C}}=\frac{m_d}{m_s}$ for the Cabibbo angle follows provided the strong interaction global vector flavor symmetry is spontaneously broken.