Magnetically induced optical self-pulsing has been observed in a Fabry-Perot resonator containing sodium vapor. Experiments are performed on optically pumped Zeeman sub-levels of the Na ground state in the presence of a static transverse magnetic field $B$. When $B$ exceeds a critical value $B_{\mathrm{cr}}$, self-sustained spin precession occurs, and the transmitted light is found to be modulated at about the Larmor frequency. The use of this tunable current-controlled oscillator in optical FM signal transmission is demonstrated.

Lateral Goos-Hänchen shifts can be increased by factors of 10-100 for laser frequency near an exciton-polariton resonance in semiconductors. A "negative" shift can occur for laser frequency ${\omega }_L$ in the pseudogap ${\omega }_0<{\omega }_L<{\omega }_l$. Surface irregularities can be probed with this effect.

Tandem-mirror plasma with sloshing-ion end plugs has been produced. Ion-velocity distribution functions are peaked at 47° to the magnetic field lines. Low-level ion-cyclotron fluctuations were detected at 1.8 times the plug-midplane frequency and with properties predicted by theory; they did not degrade plasma confinement in the plugs or central cell.

The nematic-isotropic and the nematic-to-lamellar phase changes in the lyotropic liquid crystal formed by decylammonium chloride micelles in a water-ammonium chloride solution have been studied by light scattering. The former transition shows behavior identical to that observed in thermotropic liquid crystals. The nematic-lamellar transition appears closely similar to a thermotropic nematic-smectic-$A$ change and the elastic constants diverge according to the analogy to superfluid helium and the three-dimensional $\mathrm{xy}$ model.

Quantum mechanical calculations of the ground states of droplets of $N$ atoms of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are reported. The calculations have been made by the variational Monte Carlo method for $4<~N<~728$ and by the Green's function Monte Carlo method for $3<~N<~112$. The energies, rms radii, and density distributions are reported; liquid-drop fits to the energies and radii are discussed.

Vibrational energy shifts have been observed for the substitutionally disordered $p(1\mathrm{}\times 1)(\mathrm{H}+\mathrm{D})$ and $c(2\mathrm{}\times 2)(\mathrm{H}+\mathrm{D})$ structures on Pd(100). Between 0 and 1 hydrogen concentration the hydrogen vibrational energy shifts by 3.5 and 0.5 meV for the $p(1\mathrm{}\times 1)$ and $c(2\mathrm{}\times 2)$ structures, respectively. It is argued that the relatively large energy shift of the $p(1\mathrm{}\times 1)$ structure is mainly due to adatom-adatom interaction mediated by the metal electrons.

A simple formalism is presented, within the density-functional approach, which constitutes a powerful scheme for directly calculating the ground-state energy of systems with arbitrarily located nuclei and their accompanying electrons. The method permits simultaneous relaxation of both the atomic geometries and the electronic charge densities of polyatomic systems towards equilibrium. It circumvents the far less efficient indirect (consecutive) approach in which the equilibrium geometry is determined after calculation of energies on the Born-Oppenheimer surface.

The energy distribution of sputtered metastable Ca atoms in the ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ sublevel of the lowest-lying triplet state has been measured by Doppler-shift laser-fluorescence spectroscopy. The energy distribution was found to peak at values higher than known for sputtered ground-state atoms. No threshold energy has been found. With increasing oxygen partial pressure the flux of sputtered metastable atoms increased by an order of magnitude; however, the shape of the energy distribution remained unchanged.

The nature of photogenerated charge carriers in ${\left(\mathrm{CH}\right)}_x$ is explored through the photoconductive and photovoltaic response of the polymer. Experimental results are discussed in the context of the soliton model of charge carriers. It is concluded that photogenerated charged soliton pairs may play a role in ${\left(\mathrm{CH}\right)}_x$ photoconductivity but cannot produce the observed photovoltaic response of ${\left(\mathrm{CH}\right)}_x$ devices.

A model for Ce impurities is considered, consisting of the $4f^0$ singlet and a multiplet of total angular momentum $j$ of the $4f^1$ configuration hybridized with conduction states of the metal ($U\to \infty$ limit of Anderson's model). The model is solved by a Bethe Ansatz and exact expressions for ground-state properties, e.g., valence, spin and charge susceptibilities, and resistivity, are given.

Anomalous evolution of the silicon valence-band photoemission spectra is observed in the photon energy region from the $2p$ core-excitation threshold to about 3 eV above the threshold. The $3p$-like topmost emission band shows a Fano-type resonance, and stronger intensity enhancement is observed in the deeper binding-energy region around 7.6 eV. The present results show the existence of a decaying localized core exciton at the $2p$ core-excitation threshold.

The enhancement of photochemical reactions on surface-supported metallic particles is reported. The result is obtained by uv photodissociation of organometallic molecules adsorbed on the supporting surface. Transmission electron-microscope micrographs of the resulting photodeposited film reveal enhanced deposition on and near the metal particles, and a clear interference pattern resulting from the mixing of the incident and reradiated light. The importance of the particle plasma resonance is described.

Electron or excitation transfer can be enhanced during vibrational relaxation after optical excitation of a donor. When it occurs after vibrational relaxation with a thermal activation energy $E_A$, enhanced transfer during vibrational relaxation is also governed by an activation energy $E_H$ which, however, is smaller than $E_A$ or even vanishes. The decrement $E_A-E_H$ depends on the total energy of vibrations triggered by optical excitation, and also on their average direction relative to that of the activation barrier for transfer in the phonon-coordinate space.

A method is proposed for the approximate numerical solution of operator field equations on a lattice.

Pair production of a very heavy flavor like top leads to large-$p_T$ isolated electrons back to back with jets as observed by Arnison et al. With a top-quark mass ∼ 35 GeV, one can account for all the experimental features of these single-jet events available so far. Further tests for this interpretation are suggested.

The total momentum and transverse momentum spectra of electrons in $e^{+}{e}^{-}$ annihilation at 29 GeV have been measured. The inclusive cross section is determined to be 14.4±1.6±5.2 pb for momenta greater than 2 GeV/c. The average semielectronic branching ratios of charm and bottom quarks are measured to be (6.3±1.2±2.1)% and (11.6±2.1±1.7)%, respectively. The fragmentation function for bottom quarks is determined to be peaked at high $z$, with ${〈z〉}_b=0.75\mathrm{}\pm 0.05\pm 0.04$.

The positron spectrum from the decay ${\pi }^{+}\to e^{+}{\nu }_e$ has been examined for evidence of peaks arising from an admixture in the ${\nu }_e$ weak eigenstate of massive neutrinos. Limits on the intensity of such peaks, together with the measured $\pi \to e\nu$ branching ratio, have been used to derive constraints on the neutrino mixing parameters over the range $4 \mathrm{MeV}<m\left(\nu \right)<\mathrm{}135\mathrm{} \mathrm{MeV}$.

The existence of a second-order phase transition associated with spontaneous supersymmetry breaking in a prototype globally supersymmetric model with a conserved fermion number is demonstrated. The model is solved exactly and it is shown that one of the superfields develops a vacuum expectation value below a critical temperature and that the ground-state energy is nonzero.

Topological obstructions to the definition of unbroken-symmetry transformations in the presence of monopoles with non-Abelian flux are exposed. Consequences for color and electroweak SU(2) in the context of the SU(5) model are discussed.

It is shown how, in the large-$N$ limit of $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ gauge theory, a local symmetry can be truly broken. This is illustrated by use of the exact solution of the two-dimensional theory in the presence of a vanishingly small symmetry-breaking source term. The model is also solved at finite $N$ in order to study the approach to $N=\infty$. It is found that any finite-dimensional subgroup of $\mathrm{SU}\left(\infty \right)$ can be broken.