We have realized total electromagnetic mode confinement in a microscopic optical, Casimir-type, cavity and detected the resonant change of the molecular fluorescence time under short-pulse excitation due to a spontaneous-atomic-decay enhancement-inhibition process (Purcell effect). This corresponds to the first realization in optics of the resonant coupling of atoms with a single mode of the radiation field.

We have calculated oscillator strengths for transitions between low-lying states of the alkaline-earth atoms using both configuration-interaction (CI) and simple optimized molecular rotor-vibrator (RV) wave functions for the $e$-core-$e$ system. Our CI results compare favorably with experimental and other accurate values, indicating that these functions used in previous studies of electron correlation are reliably accurate. Most RV results agree better with accurate values than do Hartree-Fock results, thus showing the success of the RV model in its first test of calculating an experimental observable.

A new method is described in which Li atoms are excited and aligned by pumping of the Li $1s^{2}2s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}\to 1s^{2}2p{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2},\frac{3}{2}}^{}{}_{}{}^{}$ transitions with a linearly polarized dye-laser beam, and subsequently raised to core-excited $1snl{n}^{\prime }{l}^{\prime }{}_{}{}^2{}_{}{}^{}S$, ${}_{}{}^2{}_{}{}^{}P$, ${}_{}{}^2{}_{}{}^{}D$ states by linearly polarized synchrotron radiation. The intensity of the electrons ejected upon the Li $1snl{n}^{\prime }{l}^{\prime }{}_{}{}^2{}_{}{}^{}S$, ${}_{}{}^2{}_{}{}^{}D\to 1s^2{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}\epsilon l$ autoionization strongly varied with the character of the core-excited state, the intermediate ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ or ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ state, and the angle between the polarization vectors of the two photon beams.

We measure the velocity dependence of the capillary pressure, $\Delta P_c\mathrm{}\left(v\right)\mathrm{}$, between two fluids in a porous medium. At zero velocity, the interface is pinned, and a critical $\Delta P_c$ must be achieved before the interface moves. For nonzero velocities, there is an additional dynamic component to $\Delta P_c$, which scales as $v^{\frac{1}{2}}$ when a wetting fluid displaces a nonwetting fluid. We suggest that this dynamic component of $\Delta P_c$ can stabilize viscous fingers, and obtain excellent agreement with experiment.

The theory and first nonlinear simulations of the Rayleigh-Taylor instability in the limit of large ion Larmor radius are presented. It is shown that in the limit of large Larmor radius, the Rayleigh-Taylor instability evolves much faster and in a dramatically different manner than in the limit of small Larmor radius.

The anisotropic temperature relaxation rate is obtained from the measured time evolution of $T_{\perp }$ and $T_{\parallel }$ in a magnetized plasma consisting of only electrons. The velocity-space anisotropy is induced by an essentially one-dimensional compression (or expansion) which changes $T_{\parallel }$ but not $T_{\perp }$. $T_{\perp }$ and $T_{\parallel }$ are then measured as they relax to a common value. The relaxation rate is obtained as a function of plasma density and temperature. Good agreement with collisional Fokker-Planck theory is found over a range of two decades.

The propagation of waves in a superfluid Fermi liquid is discussed in the quasiclassical regime on the basis of a nonlinear kinetic equation. We show that the dominant nonlinearity appears in the distribution function (rather than the mean fields) due to resonant excitations across the gap in a small regime of momentum space. The dynamics of these resonantly excited quasiparticles is governed by a Blochtype equation for a pseudospin vector in particle-hole space. We consider saturation effects and soliton formation in the sound propagation in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ in some detail and comment briefly on the $B$ phase.

We study the implications of the ideas of finite-size scaling on homogeneous nucleation phenomena near the critical solution point. It is shown that even with rather simple assumptions, the predictions of classical nucleation theory are modified significantly, and there is indication of a lowering of the nucleation barrier.

Changes in shear elastic constant, long-range order, and lattice parameter were measured during disordering and eventual amorphization of ${\mathrm{Zr}}_3$Al by ion irradiation. Large (≃50%) elastic softening was observed during disordering, and anomalies occurred in all three measured parameters over a narrow range of ion doses. The results indicate that a first-order phase transformation triggered by an elastic instability occurs during solid-state amorphization. The changes reported here during disordering and amorphization are very similar to behavior observed previously in a large number of solids during heating to melting.

The results of zero-, transverse-, and longitudinal-field muon-spin rotation measurements in polycrystalline Ce${\mathrm{Al}}_3$ are reported. They provide evidence for static magnetic correlations in Ce${\mathrm{Al}}_3$ below 2 K. From the magnitude of the local magnetic field at the muon site it was estimated that the effective ${\mathrm{Ce}}^{3+}$ moments may be of the order of 0.05${\mathrm{\mu }}_{\mathrm{B}}$. The magnetic correlations appear as a spatially inhomogeneous phenomenon, and are partly coherent below 0.7 K. No evidence for a cooperative phase transition is found.

The first measurements of the shift in position of the photoabsorption edge in a laser-heated and shocked solid material are reported. A buried tracer layer is first radiatively heated to a few electron-volts leading to the appearance of bound-bound transitions near to the $K$ photoabsorption edge. Then as the shock runs through, the $K$ edge shifts to lower energy ionizing the bound-bound transitions, in agreement with theory.

We present a method to compute dynamical correlation functions in quantum many-body systems at zero temperature. The ground state of a finite system is evaluated exactly by a modified Lanczos method and from it the real-frequency correlation functions are obtained by a projective technique for the memory-function formalism. We apply the method to the density-density correlation function of a one-dimensional spinless fermion system. Exact results are recovered in the noninteracting limit; in the strong-coupling limit our results are compared with Monte Carlo simulation and analytical approximations.

We have measured photoelectron energy spectra from thin Na and Ba overlayers on Cu(111). The spectra show extremely narrow adsorbate-induced peaks, much narrower than observed for any other adsorbate system. These features arise from electrons trapped in the potential well between the vacuum barrier and the Cu(111) surface which has a high electron reflectivity for energies within the band gap producing the necks of the Cu Fermi surface.

Spin-lattice relaxation experiments on single nuclear-spin-polarized ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ atoms chemisorbed on (hot) metal surfaces yield direct information on the local density of states at the Fermi energy, a quantity of high general and actual interest.

We report the first observation of the complete quenching of the Hall effect in a one-dimensional conductor. In our narrowest wires at low temperatures and for small magnetic fields, where the 1D subband splittings exceed both $k_{\mathrm{B}}T$ and $\hslash {\omega }_c$, we observe striking departures from the 2D Hall effect, characterized by an unexpected low-field plateau and a precipitous, complete suppression of the Hall resistance. We believe these to be unambiguous manifestations of one-dimensional electrical transport; they appear to provide a direct measure of the number of quantum conduction channels that participate.

The Davey-Stewartson I equation is a nonlinear evolution equation originally derived in the context of multidimensional, weakly nonlinear water waves. It has recently been exactly solved by the classical inverse-scattering method for localized potentials, and also possesses nonlocal soliton solutions. We have calculated Poisson-bracket relations for elements of the scattering matrix, as well as corresponding quantum commutation relations. Commutation relations are found that are a (2+1)-dimensional generalization of a Yang-Baxter algebra.

It is shown that (0,2) Calabi-Yau manifolds as exact solutions at the string tree level can be obtained from a class of (2,2) Calabi-Yau manifolds, which are constructed as blown-up $Z_n$ orbifolds.

We have searched for the decay process $K^{+}\to {\pi }^{+}{A}^0$, where $A^0$ is any particle of mass less than 100 MeV/${\mathit{c}}^2$ decaying into $e^{+}{e}^{-}$. Upper limits for the branching ratio are given as a function of mass and lifetime of the $A^0$. For lifetimes shorter than ${10}^{-13\mathrm{}}$ sec, a limit of 4.5×${10}^{-7\mathrm{}}$ at the 90% confidence level is obtained.

We calculate classical skyrmion collisions in 3+1 dimensions. Numerical integration of Hamilton's equations for the chiral fields is based on a staggered leap-frog method. We study collisions of defensive hedgehog solitons at various impact parameters for center-of-mass energies of 157, 432, and 885 MeV. Internal excitations of the skyrmions and meson emission are observed. The time evolution of the pion field and momentum and baryon densities is shown, as are deflection functions and inelasticities. Some results for skyrmion-antiskyrmion annihilation are presented.

Cross sections and $T_{20}$ analyzing powers for $\mathrm{dA}\to \mathrm{pX}$ are presented. A shoulder in the cross section previously reported at higher energies and for carbon is observed for H, C, and Ti at the same $d$-c.m.-frame proton momentum, $q=0.35\mathrm{}$ GeV/c. At $q<\mathrm{}0.2\mathrm{}$ GeV/c both cross-section and $T_{20}$ data depend only weakly upon the target atomic number $A$. Calculations in the plane-wave impulse approximation with several $\mathrm{NN}$ wave functions, and with either a $\Delta \Delta$ or a six-quark component added, are discussed.