An array of capacitive probes is used to measure the spatially dependent electric field associated with a driven chaotic instability in p-type ultrapure Ge. As the drive amplitude is increased, we observe first the onset of temporal chaos and later a transition to a higher-dimensional attractor with a loss of spatial coherence due to the nucleation and destruction of high-field domains in the bulk of the sample.

Temperature and kinematic line broadening are the primary contributions to the width of the proton energy spectrum measured in cluster-impact fusion experiments. By ascertaining these two contributions, we have determined an effective temperature for the high-velocity deuteron component that is responsible for the measured fusion yield. The extracted effective temperature is substantially higher than conventional estimates, and implies that cluster-impact fusion is hot fusion on an atomic scale. The proton spectrum rules out contaminants in explaining the high yield.

The perturbed γγ angular correlation method has been used to study diffusion and desorption of isolated ${}_{}{}^{111}{}_{}{}^{}\mathrm{In}$ atoms adsorbed on a Si(111)7×7 surface. Two different adsorption sites are found and their hyperfine parameters are determined as a function of temperature and compared to first-principles calculations. The activation energy for the migration to regular adsorption sites is determined to 0.72(5) eV. The relative population of the two adsorption sites changes at about 500 K corresponding to an activation energy of 1.61(15) eV for this process. The binding energy of the indium atoms is estimated to 1.93(10) eV. The desorption behavior is found to be strongly dependent on In concentration in the low coverage regime.

The dynamics in an ethanol glass at 1.5 K has been investigated from picoseconds to milliseconds by two-dimensional stimulated-photon-echo measurements on zinc porphin. In this time frame the distribution of relaxation rates exhibits a 1/R dependence except for a gap stretching from about 1 kHz to 1 MHz. Evidence is presented for a time evolution of the glass structure that is not accounted for in the standard two-level-system model.

The single-particle electronic structure of a two-dimensional electron gas in a nonuniform magnetic field B consists of states that propagate perpendicularly to the field gradient ∇B and have a remarkable time-reversal asymmetry. In one of the allowed directions the propagation has free-electron character and is confined to a narrow one-dimensional channel localized about the region where ‖B‖ is minimum. In the opposite direction, the Landau states propagate throughout the rest of the sample with a velocity proportional to ‖∇B${\mathrm{\Vert }}^{1/2}$.

We report the first direct measurement of the relaxation of plasma oscillations in a solid. Via the second-harmonic autocorrelation of femtosecond laser pulses, the lifetimes of localized plasma oscillations in silver island films were investigated. Decay times of 40±7 fs were obtained, which indicate that single-particle scattering is mainly responsible for the energy relaxation of the plasma oscillations.

Model colloids composed of two widely separated sizes of poly- styrene spheres are studied at high volume fractions using an optical, multiple-scattering technique. These measurements probe hydrodynamic forces between unlike particles, as well as static, structural predictions made using the Percus-Yevick approximation. The dynamic data corroborate currently available hydrodynamic theories on very short length scales; the dynamic data also reveal a new, experimentally accessible range of intermediate length scales which currently available theories cannot explain.

We report uniformly scaling rotor solutions of the free-boundary problem of wave propagation in reaction-diffusion models of single-diffusive excitable-oscillatory media with a unique wavelength and rotation frequency obeying the Fife scaling λ∼${\mathrm{\epsilon }}^{2/3}$ and ω∼${\mathrm{\epsilon }}^{\mathrm{-}1/3}$. In simulation of the models, the small-ε rotation regime appears to always be non-steady-state but, remarkably, it remains partially describable in terms of these solutions.

We formulate the problem of finding the spiral core which smoothly matches onto the asymptotic rotating solution of the FitzHugh-Nagumo model. We prove that the inner problem (with scale ε, the ratio of the reaction rates) has a solution for all possible outer solutions on scale ${\mathrm{\epsilon }}^{2/3}$; furthermore, we explicitly determine this solution via a simple numerical procedure. This completes the rigorous demonstration of the existence of rotating spiral solutions in singly diffusive excitable systems.

We study a tetrafunctional network of freely jointed rigid rods in two dimensions and show that, at equilibrium, it will be in a highly swollen state. Surprisingly, such a network is a critical object with large crosslink density fluctuations on all length scales and anomalously low shear modulus. These conclusions are very different from the classical picture and raise questions of how large are crosslink fluctuations in real gels and rubbers.

The geminate rebinding kinetics of MbCO in solution at high temperature (260–300 K) shows nonexponential behavior (stretched, β∼1/2) that may be related to nonequilibrium relaxation of the distal pocket. A two-pulse photolysis experiment, which probes a kinetically selected subpopulation, demonstrates that the nonexponential behavior arises from a fluctuationally averaged system and also reveals slow interconversion times for large-scale protein motions. Measurements as a function of temperature lead to a direct determination of the Arrhenius barrier at the heme (18±2 kJ/mole).

We have measured the ratio of nuclear spin-precession frequencies of ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ and ${}_{}{}^{201}{}_{}{}^{}\mathrm{Hg}$ atoms for two orientations of magnetic field relative to the Earth’s gravitational field. We find that the spin-dependent component of gravitational energy is less than 2.2×${10}^{\mathrm{-}21}$ eV, a substantial improvement over previous limits. Our result provides a test of the equivalence principle for nuclear spins, and sets limits on the magnitude of possible scalar-pseudoscalar interactions which would couple to the spins.

The general parametrization method [Phys. Rev. D 40, 2997 (1989)] (an exact consequence of a QCD-like relativistic field theory) is used to parametrize the masses of 8 and 10 baryons to second order in flavor breaking. Because at first order in flavor breaking, three-quark contributions to octet masses are very small, we neglect such contributions at second order and derive a ‘‘corrected’’ Gell-Mann–Okubo formula; when written in a way free from electromagnetic corrections, it is 1/2(n+${\mathrm{\Xi }}^0$)+T=1/4(3Λ+${\mathrm{\Sigma }}^{+}$) with T=${\mathrm{\Xi }}^{\mathrm{*}\mathrm{-}}$-1/2(Ω+${\mathrm{\Sigma }}^{\mathrm{*}\mathrm{-}}$) and Σ^ ${}_{}{}^{+}{}_{}{}^{}$=2${\mathrm{\Sigma }}^{+}$-${\mathrm{\Sigma }}^0$+2(n-p). The two sides of the formula are respectively 1132.4±0.8 and 1133.9±0.1 MeV.

An explanation is proposed to the problem why the πNN form factor known from NN analysis is by far harder than the one obtined in theoretical subhadronic models for nucleon structure. The soft πNN form factor compatible with the models is allowed for the NN interaction by considering the additional contribution due to the exchange of the correlated three-pion state of I=1, ${\mathit{J}}^{\mathit{P}}$=$0^{\mathrm{-}}$ between the two nucleons. The same mechanism explains consistently the axail-vector form factor.

The statistical decay of an equilibrated hot nucleus is modeled by sampling the microcanonical phase space for nuclear fragmentation. It is shown to reproduce the measured fluctuations and correlations (intermittency) in data for 1 GeV/nucleon ${}_{79}{}^{197}{}_{}{}^{}\mathrm{Au}$ on emulsion. Within our model multifragmentation is linked to the nuclear liquid-to-gas phase transition. The model is used to realistically study the conditions leading to the phenomenon of intermittency in critical heavy-ion reactions.

Strong direct processes were observed for elastic breakup in 54-MeV ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$${+}^{12}$C ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ reactions. In the case of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, the observed ${}_{}{}^7{}_{}{}^{}\mathrm{\alpha }$+t direct-breakup yield was significantly larger than predicted by a Coulomb-breakup calculation, indicating the importance of the nuclear field. For ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, final-state interactions produced a strong distortion in the fragment energy spectra, as well as a modulation of the coincidence efficiency for different detector geometries. Such Coulomb effects are found to severely complicate the extraction of radiative-capture cross sections from direct-breakup data.

Spectroscopy of superdeformed nuclear states opens up an exciting possibility to probe new properties of the nuclear mean field. In particular, the unusually deformed atomic nucleus can serve as a microscopic laboratory of quantum-mechanical symmetries of a three-dimensional harmonic oscillator. The quantum numbers and coupling schemes characteristic of weakly deformed systems are expected to be modified in the superdeformed world. New classification schemes can be directly related to certain geometrical properties of the nuclear shape.

In order to investigate whether entrance-channel effects influence the production of superdeformed nuclei, we have measured the yield of the yrast superdeformed band in ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ populated via nearly mass-symmetric ${(}^{82}$Se${+}^{74}$Ge) and mass-asymmetric ${(}^{48}$Ca${+}^{108}$Pd, ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$${+}^{120}$Sn) fusion reactions leading to the same compound nucleus at similar excitation energies and angular momenta. Large differences in the relative intensity of the band compared with the total yield of the nucleus are observed in the various reactions. This effect indicates that the competition between fission and neutron evaporation is affected by the mode of formation of the fusing system.

A strong right-left scattering asymmetry, depending on scattering angle, has been observed for electron capture by protons impinging on circular states of Na(3P), excited by circularly polarized light incident perpendicular to the scattering plane. Scattering angles are extremely small, corresponding to grazing incidence collisions. Proton energy is 1 keV, i.e., a collision velocity about half of the orbital velocity of the sodium 3p electron. The observed asymmetry agrees with recent elaborate theoretical predictions using large atomic basis sets.

We present experimental measurements of harmonic generation in xenon using a 1064-nm 40-psec Nd-doped yttrium aluminum garnet laser. The harmonic yield is studied as a function of the position of the laser focus in the atomic beam. It shows regular oscillations whose period decreases with increasing harmonic order and which can be interpreted as phase-matching effects due to the tight focusing geometry. Moreover, the amplitudes of the oscillations vary rapidly with the laser intensity, a signature of resonance effects in the harmonic generation process.