We report measurements of the hyperfine structure of the 6$P_{3/2}$ state of atomic ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$(I=7/2). A frequency-stabilized laser diode is used to perform crossed-beam laser spectroscopy of the Cs 6$S_{1/2}$(F=3,4)→6$P_{3/2}$(F’) transitions. From the measured hyperfine splittings, we determine the coefficients of the magnetic dipole (A) and electric quadrupole (B) contributions to the hyperfine structure. Our results are A=50.275(3) MHz and B=-0.53(2) MHz.

A comparison is made of two recently suggested approximate analytical methods for the investigation of nonlinear pulse propagation in optical fibers, as described by the nonlinear Schrödinger (NLS) equation. One approach is based on a variational procedure involving Ritz’s optimization while the other makes use of invariants of the NLS equation. Despite their different character the approximation schemes are shown to lead to identical results for the evolution of the pulse amplitude and pulse width.

We calculate the vacuum-field radiation pressure on two parallel, perfectly conducting plates. The modes outside the plates push the plates together, those confined between the plates push them apart, and the net effect is the well-known Casimir force. Implications of this result for the form of the Poynting vector in quantum electrodynamics are discussed.

A new mechanism is proposed for atomic recombination in plasmas, whereby the binding energy is carried away by a plasmon. It is suggested that this mechanism may compete with radiative and three-body modes in the case of recombination to sufficiently highly excited and perturbed states of hydrogen. A procedure for calculation of the transition rate is outlined in a model which treats the plasma oscillations by the Bohm-Pines canonical transformation and the atomic bound states by a second canonical transformation.

Transient local hexagonal order in a dense liquid is observed in a molecular-dynamics simulation of two-dimensional soft disks. Instantaneous local structure factors at a particular density are obtained using an optical transform of the particle coordinates for a single configuration. Local hexagonal order is quantified using an order parameter, and its lifetime characterized by the decay of the order-parameter autocorrelation function. This type of transient structure is significant at densities greater than (7/10 of the freezing density, and becomes persistent near the freezing density.

We define the extended Schrödinger equation as the integro-differential equation having a nonlocal potential which is an extension of a given local potential and investigate the behavior of the length of nonlocality as a critical parameter that separates a ‘‘phase’’ of localized energy eigenfunctions from another unlocalized one.

We explain discrepancies between a recent Rapid Communication by Zheng and an earlier paper by Friedberg. The earlier results are correct. The discrepancies are due to differences of method rather than inaccuracies of detail.

The effective potential previously introduced by the variational method is used to calculate thermodynamic quantities of quantum one-dimensional nonlinear fields in the weak-coupling approximation. The correct continuum limit is recovered both for integrable (sine-Gordon) and noninte- grable (${\phi }^4$) models. Good agreement is found with exact Bethe-ansatz results for the specific heat.

We examine the criteria of Kadanoff and Baym for the validity of local differential conservation laws for particle number, momentum, and energy in the framework of equations of motion for Green’s functions. For energy conservation an additional relation for the total time derivative of the two-body Green’s function is needed. The stress tensor and the heat current density are generalized to nonlocal interactions and arbitrary perturbations.

An inductance-resistance diode circuit with square-wave input shows period-doubling and chaotic behaviors similar to a circuit with sinusoidal-wave input. These near-resonance phenomena using a fast-recovery diode agree well with our theoretical model that includes neither diffusion capacitance nor reverse recovery time but only includes the varactor characteristics of the junction capacitance. Computer solutions and experiments show only period-doubling 2T bifurcations which agree very well with each other.

A method is described for reducing noise levels in certain experimental time series. An attractor is reconstructed from the data using the time-delay embedding method. The method produces a new, slightly altered time series which is more consistent with the dynamics on the corresponding phase-space attractor. Numerical experiments with the two-dimensional Ikeda laser map and power spectra from weakly turbulent Couette-Taylor flow suggest that the method can reduce noise levels up to a factor of 10.

The critical behavior of the electroclinic effect above the transition from the smectic-A to the chiral smectic-$C^{\mathrm{*}}$ phase has been studied using the experimental geometry of a surface-stabilized ferroelectric liquid-crystal cell. The value of the tilt susceptibility exponent γ is found to be 1.04±0.05, consistent with the mean-field description of this transition.

The disagreement between Shelton’s result [Phys. Rev. A 36, 3461 (1987)] for the rotational hyperpolarizability in the dc Kerr effect and that of previous workers [A. D. Buckingham and B. J. Orr, Proc. R. Soc. London, Ser. A 305, 259 (1968); A. D. Buckingham, Proc. R. Soc. London, Ser. A 267, 271 (1962)] is resolved in favor of the latter.

Yurke and Potasek [Phys. Rev. A 36, 3464 (1987)] have shown that pure states of correlated pairs of quantum systems can lead to mixed-state behavior if only one of the systems is observed. We note that such behavior is well known and describe how the mixed-state properties of these states have led to their application in thermodynamical problems via the thermofield formalism. The correlations have been found to lead to manifestly nonclassical behavior (such as squeezing) if both systems are observed.

The integral alignment of $\mathrm{H}\mathrm{}\left(2p\right)\mathrm{}$ was measured for 1-25-keV ${\mathrm{H}}^{+}$-H,${\mathrm{H}}_2$ collisions. At incident energies of a few keV, $\mathrm{H}\mathrm{}\left(2p\right)\mathrm{}$ production is the result of a united-atom $2p\sigma -2p\pi$ rotational coupling. The experimental results for ${\mathrm{H}}^{+}$-H are in reasonable agreement with numerical calculations by W. Fritsch and C.-D. Lin [Phys. Rev. A 26, 762 (1982); 27, 3361 (1983)].