Four new neutron-rich, fission-product nuclei have been identified at the on-line mass separator TRISTAN at Brookhaven National Laboratory. Their half-lives have been measured to be, for ${}_{}{}^{156}{}_{}{}^{}\mathrm{Pm}$, $T_{\frac{1}{2}}=28.2\mathrm{}\pm 1.1$ sec; for ${}_{}{}^{159}{}_{}{}^{}\mathrm{Sm}$, $T_{\frac{1}{2}}=15\mathrm{}\pm 2$ sec; for ${}_{}{}^{160}{}_{}{}^{}\mathrm{Sm}$, $T_{\frac{1}{2}}=8.7\mathrm{}\pm 1.4$ sec; and for ${}_{}{}^{161}{}_{}{}^{}\mathrm{Eu}$, $T_{\frac{1}{2}}=27\mathrm{}\pm 3$ sec. These nuclei are of particular importance in nucleosynthesis calculations, since they lie in the region of the rare-earth maximum in $r$ process abundances. A comparison of these and other new half-lives with recent calculations discloses a characteristic pattern of discrepancies.

Size distributions of fragments from multiply charged clusters have been determined. On a time scale of 0.1 ms with respect to ionization, triply charged C${\mathrm{O}}_2$ clusters of size $n\approx 114$ are found to fission extremely asymmetrically, their doubly charged fragments carrying 92% of the mass. For doubly charged C${\mathrm{O}}_2$ clusters, however, evaporation of neutral monomers is the only channel for delayed dissociation. A model, based on the liquid-drop approximation, can quantitatively account for the lower size limits of multiply charged clusters as well as for the distribution of fission fragments from (C${\mathrm{O}}_2$) ≅${114}^{3+}$.

The phase-space distribution function corresponding to a ground-state density of a many-electron system proposed earlier is explored as a means for generation of momentum-space properties through density-functional theory. Excellent results are found for the spherically averaged Compton profiles for several atoms and the molecules ${\mathrm{H}}_2$ and ${\mathrm{N}}_2$, as well as the directional Compton profiles for ${\mathrm{N}}_2$, thereby providing both a useful scheme for computation of such profiles and confirmation of the basic theory. The entropy-maximization procedure employed is discussed from the point of view of information theory.

By application of the Coulomb-explosion technique with a new type of detection system, the structure of the neutral ${\mathrm{C}}_3$ molecule has been studied. The detector allows for the first time simultaneous determination of the velocity vectors of all nuclei involved, from which correlation between internal degrees of freedom in the molecules can be derived.

Double sets of $m=1\mathrm{}$ helical coils fed by appropriately phased radio-frequency currents are shown theoretically to be capable of driving both toroidal and poloidal currents in a toroidal plasma by means of the nonlinear Hall effect. It is shown that total toroidal current is optimized when the ratio of the plasma circumference to the pitch length of the helical coils is 1.35.

Results from a Raman free-electron-laser oscillator producing Å2 MW at 2.5-mm wavelength ($\frac{\Delta \lambda }{\lambda }\simeq 1\%$) are reported. A novel method of extracting regenerative-gain and power-coupling-loss measurements from signal delay times is described and the experimental analysis compared with 3D theory. The first observation of long-wavelength sideband power in the Raman regime is reported at high undulator strength. Temporal behavior of the output after saturation is reached is discussed.

The Chapman-Enskog expansion for a fluid in uniform shear flow is investigated with use of a Bhatnagar-Gross-Krook model for the nonlinear Boltzmann equation. It is shown that an expansion of the pressure tensor in powers of the uniformity parameter (the shear rate) about the origin does not converge for hard spheres. However, a convergent expansion about the point at infinity can be used to establish that this Chapman-Enskog expansion is asymptotic.

Neutron yields in excess of ${10}^{12}$ were achieved with the twelve-beam green GEKKO XII laser by choice of a shock-multiplexing imposion mode as predicted by a simulation code HIMICO. The first half of a Gaussian pulse was used to achieve a tailored implosion with shock multiplexing. The implosion mode is sensitive to the matching between the implosion time and the laser pulse. The simulation result suggests that the compression with a large deceleration at the stagnation phase due to the shock-wave multiplexing plays an important role in attainment of high neutron yields without pusher-fuel mixing in high-aspect-ratio D-T shell targets.

Heat-capacity measurements of ethylene on graphite in both the submonolayer and monolayer regions reveal a weak and broad anomaly relating to the melting transition of the overlayer. The findings in the submonolayer are in contrast to all previous studies in physisorbed systems, where sharp heat-capacity signals were observed. These results suggest that the melting of ethylene on graphite is a continuous transition for submonolayer as well as monolayer coverages.

Ab initio all-electron calculations for carbon and oxygen chemisorbed on nickel clusters indicate that the charge redistribution induced by the adsorbate causes repulsive stresses between the metal surface atoms. Using lattice-dynamics calculations we show that these stresses can account for the observed $S_4$-phonon anomaly with $c(2\mathrm{}\times 2)$ oxygen overlayers, and also explain the carbon-induced surface reconstruction, via a softening of the $A_2$ mode at $X$ The reconstruction has also been reproduced directly by total-energy calculations with use of a suitable cluster.

The nuclear magnetic specific heat of bcc solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ of molar volume 24.15 ${\mathrm{cm}}^3$/mole has been measured as a function of temperature $T$ and magnetic field $B$ for $0.6 \mathrm{mK} <T<\mathrm{}40\mathrm{} \mathrm{mK}$ and $B<\mathrm{}8.0\mathrm{}$ T. The discontinuous change in entropy following the high-field to low-field phase transition has been also measured. The magnetic phase diagram has been determined. The observed specific-heat peak at the ordering temperature $T_N$ is discussed in connection with the nature of the phase transition.

The asymptotic properties of branched polymers are studied on the two- and three-dimensional Sierpinski gaskets, with use of exact recursion equations. It is shown that loops are irrelevant on large scales and the exponents $\theta$ and $\nu$ for lattice animals are obtained exactly. In the presence of self-interactions, a collapse transition occurs at a nonzero critical temperature. At the transition the value ${\nu }_t$ of the gyration-radius exponent is very close to its value in the compact phase, in analogy with recent numerical results on two-dimensional branched polymers.

We have experimentally discovered that in a nematic liquid crystal subjected to an ac electric field, the first convective structure at low frequencies is in fact a set of oblique rolls, contrary to the accepted picture. We show that it is a new structure with a helical flow motion, and thus lower in symmetry than the usual normal rolls recovered at high frequencies. Besides indicating the limitations of the available theoretical models, these results clearly show that the highest-symmetry flow structure corresponds to the normal rolls.

We present theorems on the possible sizes of ultrametric and almost-ultrametric structures and discuss implications for the entropy of spin-glasses, the traveling salesman problem, and neural network memories.

We propose a new picture of the Ising-spin-glass phase, based on an Ansatz for the scaling of low-lying large-scale-droplet excitations. We find behavior very different from the infinite-range model. The truncated spatial correlations decay as a power of distance, the ac nonlinear susceptibility diverges as a power of $\ln \omega$, and the magnetization noise power diverges as $\frac{1}{\omega }$ with logarithmic corrections. A magnetic field destroys the spin-glass phase so that there is no de Almeida-Thouless transition. Defect excitations should yield similar dynamic phenomena in vector spin-glasses.

X-ray photoemission spectroscopy was used to measure directly the CdTe-HgTe (¯1¯1¯1) heterojunction valence-band discontinuity (${\Delta E}_v$) with the result ${\Delta E}_v=0.35\mathrm{}\pm 0.06$ eV. On the basis of the frequently applied common-anion rule, it has generally been assumed that ${\Delta E}_v$ would be small; the large value of ${\Delta E}_v$ will affect predicted CdTe-HgTe heterojunction and superlattice properties. In conjunction with recent ${\Delta E}_v$ measurements on the $\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}-{\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x\mathrm{As}$ heterojunction system, the large ${\Delta E}_v$ result for the CdTe-HgTe (¯1¯1¯1) heterojunction provides direct experimental evidence in contradiction to the common-anion rule for lattice-matched heterojunction interfaces.

Laser diffraction experiments were made for colloidal crystals of highly charged polyballs in semidilute aqueous solutions at low ionic strength. Fine structures with line uncrossings and splittings were observed at otherwise intersecting points of Kossel rings. Analysis of these anomalies of diffraction patterns leads to the interpretation that the Kossel images including their fine structures are direct manifestations of the loci of gaps of the dispersion surface at the Brillouin-zone boundaries.

We discuss finite-size effects on symmetry breaking in curved space-times with some compact dimensions, and the implications for inflationary cosmologies. Infrared behavior in the de Sitter universe is studied by examination of the lowest-mode contribution to the effective potential for an $N$-component scalar field. We find that at the Planck energy the shape of the effective potential near the symmetric state can significantly deviate from the overall flatness condition necessary for the implementation of new inflation. This effect can in principle rule out Planck-scale inflationary transitions.

It is shown that a bunch of charged particles following a curved path in a magnetic field is subject to a force due to its own electromagnetic field. One aspect of this is a "centrifugal" force acting on individual particles in the bunch. A resonance mechanism, capable of disrupting the beam at modest currents, is given as an example of the importance of this force. The theory is tested with observations from the Cornell Electron Storage Ring. This force will cause important modifications to existing theories of accelerator stability.

The Floquet solution for the evolution operator of a periodically time-dependent two-level Hamiltonian provides an effective Hamiltonian that can be used to examine the equilibrium properties of the system. In one example, calculations with a model Hamiltonian show that identical equilibrium properties are predicted in the laboratory frame as in a time-dependent interaction frame. A second example considers the changes that arise when the model Hamiltonian contains an explicit periodic time dependence.