A theory of excitons in a high magnetic field normal to the confining quantum well of III-V semiconductors is constructed. The theory dictates that all the observable optical transitions must involve bound excitons, that the field dependence is nonlinear, and that extra spectral lines arise from the mixing of heavy- and light-hole character in the Landau levels. These salient features lead to a drastic reinterpretation of the magneto-optical spectra in comparison with calculated exciton energies.

Low-intensity ${(10\mathrm{}}^{\mathrm{-}5}$–${10}^{\mathrm{-}2}$ watts/${\mathrm{cm}}^2$) IR radiation at 9–15 μm desorbs HD from 1.5–4.2-K LiF (100) at a rate (maximum 0.001 monolayer/s) proportional to the light intensity. This process is independent of temperature below 4.2 K, the velocity distribution is approximated by a temperature of 21 K, and the desorption efficiency increases with increasing wavelength. Desorption is attributed to single phonons created in a cascade following optical absorption. Thermal desorption is excluded as a possible mechanism except at high surface temperatures and coverages.

The fractal invariant measure of chaotic strange attractors can be approximated systematically by the set of unstable n-periodic orbits of increasing n. Algorithms for extracting the periodic orbits from a chaotic time series and for calculating their stabilities are presented. With this information alone, important properties like the topological entropy and the Hausdorff dimension can be calculated.

We show the dynamical generation of a composite U(1) gauge field in the SU(N,1)/SU(N)×U(1) σ model as an extension of the result of D’Adda, Di Vecchia, and Lüscher on the two-dimensional ${\mathrm{CP}}^{\mathrm{N}}$ model, and establish the noncompact model as a meaningful quantum field theory.

The lattice-gauge-theory generalization of Adler’s over-relaxed heat-bath algorithm and an over-relaxed Metropolis update are shown to accelerate the decorrelation of physical observables. The heat-bath’s microcanonical limit is especially attractive. Numerical tests for pure gauge SU(3) ($4^4$ lattice, β=5.6) show, for example, that over-relaxation reduces the Polyakov-loop magnitude autocorrelation time for the Cabibbo-Marinari algorithm from 28 sweeps to 9, increasing computational efficiency threefold. These approaches are applicable to a large class of physical systems.

The dielectric constant ε and magnetic permeability μ for gluon plasma are calculated from the one-loop gauge-invariant effective action. The real parts are gauge-fixing independent and agree with earlier work. The imaginary part of ${\mathrm{\mu }}^{\mathrm{-}1}$ is zero in any covariant background-field gauge, while the imaginary part of ε is gauge-fixing dependent and negative definite. This result indicates that there is no consistent perturbative description of gluonic plasmons on scale ≥(${\mathrm{g}}^2$T${)}^{\mathrm{-}1}$.

Let α be the relative norm of a symmetry-breaking term in the Hamiltonian of a many-particle system, and Λ the energy-dependent transition parameter which charcterizes the quantum chaos via spectral and strength fluctuations. Combining a compact theory for Λ/${\mathrm{\alpha }}^2$ with fluctuation theories by which Λ can be deduced from (neutron-resonance) data gives, for the time-reversal-noninvariant nucleon-nucleon interaction, α≤(1–2)×${10}^{\mathrm{-}3}$, which would improve with better small-strength data in nuclei with dense spectra. Diffusion equations involving Λ as the ‘‘time’’ variable are also discussed.

Spin-flip probabilities have been measured for inelastic proton scattering from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 319 MeV at angles between 3° and 12° and excitation energies up to about 40 MeV. These data can be directly related to the relative [(spin transfer)/(no spin transfer)] nuclear response via one model-dependent variable. Nuclear spin excitations appear relatively suppressed at low excitation energies but surprisingly enhanced at the highest excitation energies at intermediate angles. Many features of the data can be explained with a slab nuclear response with random-phase-approximation correlations.

We have measured the energy and angular dependence of charged-pion production, with associated multiplicity selection, in La + La collisions at 138, 183, and 246 MeV/nucleon. The pions are produced mainly in collisions with a large number of participants. The general behavior of the spectra is consistent with results at higher energies, but the yield of subthreshold pions depends much more strongly upon the target and projectile mass. The pion spectra at 246 MeV/nucleon exhibit a strong charge dependence.

A ripplelike structure in the photodetachment cross section of ${\mathrm{H}}^{\mathrm{-}}$ near threshold, arising from autocorrelation in the wave function of the photoelectron in the presence of motional electric fields, is observed.

The wave function of benzene may be described in terms of two components corresponding to the Kekulé structures. Theoretical evidence is presented which indicates that the optimal orbitals comprising these structures form alternating single bonds and double bent bonds rather than the conventional σ and π bonds. Ab initio calculations which incorporate electronic correlation effects and explicitly treat resonance demonstrate that the bent-bond description is energetically the better representation of the ground state.

We present the theory of laser-induced radiative association in terms of a scattering resonance formalism and apply this theory to the specific case of Na atom collisions at a temperature of 10 mK. Use of ultracold atoms permits a new kind of high-resolution free-bound spectroscopy for the study of near-threshold collisions and excited-state energy levels which are difficult to study by conventional bound state spectroscopy.

The multiple ionization of molecular nitrogen has been studied by use of an intense picosecond laser (0.6 ps: 3×${10}^{15}$ W/${\mathrm{cm}}^2$: wavelength 600 nm). By measurement of the energies of the various fragment atomic ions (${\mathrm{N}}^{+}$, ${\mathrm{N}}^{2+}$, and ${\mathrm{N}}^{3+}$) with a time-of-flight mass spectrometer it has proved possible to investigate the dynamics of the multielectron dissociative ionization process on a time scale of about 30 fs.

We present a high-field biased reptation model of gel electrophoresis. It is predicted that during their migration, DNA fragments can get trapped for long periods of time in near-zero–velocity, looplike compact conformations. As a consequence, the electrophoretic mobility of DNA is found to be a nonmonotonic function of the fragment size. We present experimental results showing this unique and unexpected consequence of anomalous dispersion due to DNA self-trapping in compact states.

We show that the polarizations of counterpropagating light waves in an isotropic Kerr medium are temporally unstable when their total intensity exceeds a certain threshold value. Periodic and chaotic temporal behavior can occur in the output polarizations and under certain conditions also in the output intensities.

An experiment to probe the (quasi)localization of the photon is proposed, in which optical layers are constructed following the Fibonacci sequence. The transmission coefficient has a rich structure as a function of the wavelength of light and, in fact, is multifractal. For particular wavelengths for which the resonance condition is satisfied, the light propagation has scaling with respect to the number of layers, as well as an interesting fluctuation.

A high-energy linear collider consisting of two beams, a driver beam of electrons and a high-energy beam, in which the intense low-energy driver beam is bunched, is analyzed theoretically. The low-energy beam is made to travel through resonant transfer cavities, in which it radiates microwave energy that is used to accelerate the second beam to very high energies. The low-energy beam is maintained at a constant energy by periodic induction acceleration cavities.

The shear-flow–induced distortion of the velocity distribution function of a Lennard-Jones gas is computed in a nonequilibrium molecular-dynamics simulation and compared with the kinetic theory based on the Boltzmann equation.

Phonon-imaging experiments reveal the angular distribution of high-frequency acoustic-phonon transmission through an ${\mathrm{In}}_{0.15}$${\mathrm{Ga}}_{0.85}$As/AlAs superlattice. Phonon stop bands due to Bragg reflection at the folded-zone boundary are observed for both longitudinal and fast transverse phonons. A newly predicted intrazone stop band due to coupling between acoustic modes is detected.

Anomalous reduction of the stage-I recovery is found in Ni irradiated near 10 K with 100–120-MeV Si, Cl, Br, and I ions. This reduction cannot be explained within the framework of the defect production and the radiation-annealing process only by nuclear collision. High-density electron excitations by energetic heavy ions and subsequent electron-phonon interactions play an important role in the annihilation of the stage-I interstitials.