In response to the recent announcements of evidence for room-temperature fusion in the electrolysis of ${\mathrm{D}}_2$O, we have analyzed how the fusion rate depends on the reduced mass of the fusing nuclei, the effective mass of a ‘‘heavy’’ electron, and the degree of vibrational excitation. Our results have been obtained both by accurately solving the Schrödinger equation for the hydrogen molecule and by using the WKB approximation. We find that in light of the reported d-d fusion rate, the excess heat in the experiment by Fleischmann, Pons, and Hawkins [J. Electroanal. Chem. 261, 301 (1989)] is difficult to explain in terms of conventional nuclear processes.

Electron emission from the K and L shells of carbon by 1-MeV antiproton and proton impact is studied. Double differential cross sections as a function of the electron ejection energy and angle are calculated using the continuum-distorted-wave–Eikonal-initial-state model. Contributions to the formation of a recently measured anticusp from electrons of different shells is analyzed for impact of antiprotons. The same effect is studied for the capture-to-continuum peak that appears for proton impact.

Calculations are presented for electron capture associated with pair production in collisions of heavy ions at relativistic energies. We employ the recently introduced technique of evaluating Feynman perturbation integrals exactly by Monte Carlo methods. The results agree well with virtual-photon approximations if they are carefully formulated, but appear to disagree with some published results. The cross sections for symmetric collisions of uranium, gold, iodine, copper, and silicon are presented as a function of the beam energy. These results are discussed within the context of beam storage times of a relativistic heavy-ion collider.

We show that a three-state atomic system where the upper two states have the same J and $m_J$ quantum numbers and decay radiatively to the states of a single atomic level is equivlent to the recently proposed inversionless laser system [S.E. Harris, Phys. Rev. Lett. 62, 1033 (1989)].

We study final-state interactions of the muon after muon-catalyzed D-T fusion reaction with the α particle and with target matter. The yield of convoy muons, traveling with the α particle but remaining unbound is calculated. Energy loss in the dense target may lead to capture of a fraction of these muons into outer shells of the α particle. We show that the final capture probability can be strongly density dependent.

The angular scattering of ${\mathrm{H}}^{+}$ by He has been investigated for single ionization at energies of 0.5, 1.0, and 3.0 MeV; and for double ionization at 1.0 MeV. The classical-trajectory Monte Carlo method has been used within one- and two-electron models to illustrate the collision dynamics. The angular differential single-ionization cross sections are in good agreement with experiment, and display the combined effects of proton scattering from the He nucleus and its electrons. The relative fraction of double ionization, as a function of scattering angle, shows a maximum at ∼0.9 mrad that is in agreement with the experiments of Giese and Horsdal [Phys. Rev. Lett. 60, 2018 (1988)]. This maximum is found to be due to two uncorrelated scattering events between the ${\mathrm{H}}^{+}$ and the He atom’s two electrons in the double-ionization reaction from impact parameters different than that for the single-ionization reaction.

It is shown that the probability distribution for the rotated quadrature phase [$a^{\mathrm{°}}$exp(iθ)+a exp(-iθ)]/2 can be expressed in terms of quasiprobability distributions such as P, Q, and Wigner functions and that also the reverse is true, i.e., if the probability distribution for the rotated quadrature phase is known for every θ in the interval 0≤θ<π, then the quasiprobability distributions can be obtained.

An extension of the lattice-gas automaton model for fluid equations is presented which has nonideal-gas thermodynamic properties reminiscent of first-order phase transitions. The new idea in this model is an algorithm for including interparticle potentials.

We show that a sufficiently large ac electric field reorients the smectic layers irreversibly in chiral smectic-C liquid crystals. Using uniformly aligned samples, prepared by unidirectional buffing, it is demonstrated that at a given temperature the layers tilt away from the buffing axis, b^, by an angle equal to the molecular tilt angle of the smectic-C phase. In this new configuration the molecules lie along b^ and the layers are tilted. It is also found that a small dc bias field can control the direction of the tilted layers with respect to b^. Furthermore, microscopic observations suggest that the chevron layers, common in the ferroelectric smectic-C phase, are absent after the electic field treatment which eliminates zig-zag-type defects.

Targets with a layer of aluminum buried beneath a plastic overlay have been irradiated with 0.53 μm wavelength, 20-ps pulse length light at (1–2)×${10}^{16}$ W ${\mathrm{cm}}^{\mathrm{-}2}$. The widths of Stark broadened Al xii 1$s^{21}$$S_0$–1s3p ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ spectral lines and the ratios of satellite line intensities to the Al xii 1$s^2$m ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$–1s2p ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ spectral line emitted from the aluminum layer imply electron densities up to (6–8)×${10}^{22}$ ${\mathrm{cm}}^{\mathrm{-}3}$. This result is a direct observation of significant energy transport to densities close to solid.

By means of neutron scattering the Fourier-transformed velocity autocorrelation function z(ω) of a simple fluid (hydrogen at 119 K and 768 bar) is determined for practically all frequencies ω [i.e., up to 28 ${\mathrm{ps}}^{\mathrm{-}1}$, where z(ω)=z(0)/10]. The result is consistent with the mode-coupling theory for small ω, and with the Enskog theory for large ω. The shape over the entire ω range is similar to the shape of the velocity autocorrelation function as determined from molecular-dynamics simulations.

In area-preserving maps exhibiting recurrence of Kolmogorov-Arnol’d-Moser tori, we illustrate the relationship between the recurring stability of periodic orbits and the recurrence of invariant tori. The fractal diagram is found to consist of ‘‘pagoda’’-type structures which replaces the ‘‘arches’’ of the standard map. The increase in the recurrences with the period of the orbit is explained as due to a series of bifurcation of the stable regimes inside the pagoda as well as the bifurcation of the pagoda itself. We compute some of the scaling exponents associated with the bifurcation.

We consider an island growth mechanism wherein species adsorbed on top of two-dimensional islands diffuse to the edge and are then incorporated. A simple matrix formulation is developed for this random-walk problem which allows exact calculation of the growth probability distribution, neglecting island rearrangement. Furthermore, we also show how related trapping probabilities can be calculated recursively for various stages of island growth. The case of imperfect trapping at island edges is also considered, and reduction to Eden-model–type growth in the low-trapping-probability regime is demonstrated. In general, the growing islands are rounder and have fewer defects and narrower active zones than Eden clusters.

A new cluster-growth model in which all surface sites (tip particles) of immobile clusters can evaporate with equal probability and diffuse until they stick to other clusters has been proposed and studied by using Monto Carlo simulations. This model is a multicluster version of the Botet-Jullien (BJ) model [Botet and Jullien, Phys. Rev. Lett. 55, 1943 (1985)]; particles, initially dispersed at random and later evaporated from clusters, random-walk and stick upon collision to other particles or clusters to form larger clusters. The cluster-size distribution $n_s$(t), which is the number of clusters of size s at time t, can be well represented by the dynamic scaling form $n_s$(t)∼$s^{\mathrm{-}2}$f(s/$t^z$), where z≃(1/2 in the two-dimensional case and in one dimension z≃(1/3. Moreover, the size and form of each cluster are found to fluctuate drastically throughout the growth, giving rise to the 1/f-like spectra of fluctuations of total number of the tip particles.

The transient behavior of a quadratic model system perturbed by multiplicative white noise has been investigated. The relaxation time of the system, as a function of the noise intensity D, has been determined by analog experiment and by digital simulation. The results obtained are mutually consistent, but contradict a recent theoretical prediction by H. K. Leung [Phys. Rev. A 37, 1341 (1988)] that there should be a critical slowing down of the system near the value of D for which a noise-induced transition occurs in the probability distribution. The discrepancy is resolved by deriving a new analytic result for the relaxation time, applicable to a range of systems described by separable stochastic differential equations.

Using the scanning simulation method, we study self-attracting trails (with energy ɛ per intersection) terminally attached to an im- penetrable linear boundary on a square lattice at their tricrital collapse transition. Our results for the exponents of the partition functions are ${\gamma }_1$=0.634±0.025 (one end attached to the surface) and ${\gamma }_{11}$=-0.44±0.02 (both ends attached). These values (with 95% significance limits) are within the error bars of the numerical estimates of Seno and Stella [Europhys. Lett. 7, 605 (1989)] for self-avoiding walks (SAW’s) at the FTHETA-point on the same lattice. Our results, however, differ significantly from the exact values derived by Duplantier and Saleur for SAW’s on a dilute hexagonal lattice at the FTHETA’ point. The collapse temperature $T_t$ and the tricritical growth parameter μ are very close to their analytic bounds -ɛ/$k_B$$T_t$=ln3 and μ=3.

We have calculated the electron affinities, including many-body and relativistic effects, of ${\mathrm{Mg}}^{\mathrm{-}}$ ${}_{}{}^4{}_{}{}^{}\mathrm{P}$ and ${\mathrm{Mg}}^{\mathrm{-}}$ ${}_{}{}^4{}_{}{}^{}\mathrm{°}$ to be 321 and 536 meV, respectively. The electric dipole f value for the ${}_{}{}^4{}_{}{}^{}\to _{}^4{}_{}{}^{}$S° transition is 0.3087 (length) and 0.3000 (velocity), occurring at a theoretically predicted wavelength of 2921 Å. The J=1/2→3/2 fine-structure splitting for ${\mathrm{Mg}}^{\mathrm{-}}$ ${}_{}{}^4{}_{}{}^{}\mathrm{P}$ is predicted to be 11.8 ${\mathrm{cm}}^{\mathrm{-}1}$, and the J=3/2→5/2 splitting 19.4 ${\mathrm{cm}}^{\mathrm{-}1}$. These results should help in the attempt being made by Andersen (private communiation) to observe the ${}_{}{}^4{}_{}{}^{}\to _{}^4{}_{}{}^{}$S° transition in the laboratory.

The hydrodynamic analogy for quantum mechanics is developed in a quantum phase-space representation. The key technical step in this development is the formulation of a phase-space flux (or current) density expression. Lagrangian fluid trajectories in phase space are explicitly found as solutions to a set of first-order ordinary differential equations which are formulated without making semiclassical approximation to the quantum dynamics. These fluid trajectories may be used to construct sharp structures in quantum phase space in the same way that one uses classical trajectories in classical mechanics. While these sharp structures do not themselves represent states, their properties ‘‘control’’ the dynamics of states in a manner familiar from the theory of first-order flows. The formalism reduces to Liouville dynamics in the classical limit, ħ→0. In addition to several analytic applications to the pure- and mixed-state dynamics, the approach is numerically implemented for tunneling dynamics in a double-well problem. A new picture for quantum tunneling emerges where the tunneling transport occurs when density spirals outward from one well along real-valued fluid trajectories and then into the other well. The tunneling is found to occur through localized portals, or ‘‘flux gates’’ in the phase space. We advocate the phase-space hydrodynamic model as a general tool to understand classical quantum correspondence.

Theoretical predictions for the expected Casimir or retardation energy shift Δ$E_{\mathrm{ret}(\mathrm{n}}$,l) arising from retarded two-photon exchange in a Rydberg helium atom or in Rydberg low-Z heliumlike ions have been available for some time; n and l pertain to the Rydberg electron. These systems consist of a one-electron core [nucleus and 1s electron ($e^{\mathrm{-}}$)] and a Rydberg $e^{\mathrm{-}}$. Recent experiments on the n=10 states of singly excited helium have given a weak confirmation for the presence of Casimir shifts Δ$E_{\mathrm{ret}(\mathrm{n}}$,l). High-precision confirmation is likely to come from measurements on helium, as experiments improve. Nevertheless, though probably not suitable for high-precision confirmation, a retardation effect could be very large for a system with a many-$e^{\mathrm{-}}$ core, and it might then be important to be able to at least estimate that effect. It is shown that the same formalism that was previously developed for the evaluation of Δ$E_{\mathrm{ret}(\mathrm{n}}$,l) for a one-electron (He-like) core can often be used for the many-electron core. In particular, with the core property characterized by a function F(k) (where k is the wave number of a virtual photon) related to the electric dipole polarizability, if the multi-$e^{\mathrm{-}}$ core is in an S state, we obtain essentially the same result as for helium; formally, one need merely replace the F(k) of ${\mathrm{He}}^{+}$ by the F(k) of the ion under consideration.

The extension described is largely notational. Furthermore, we show that as long as the core electrons have a spherically symmetric charge density, for a given core state or for an average over a set of core states which differ only in their angular momentum projections, the result for Δ$E_{\mathrm{ret}(\mathrm{n}}$,l) is very similar to the heliumlike result. Thus, we give several methods to estimate core properties and Δ$E_{\mathrm{ret}(\mathrm{n}}$,l) for a variety of systems and use these methods to obtain rough estimates of Δ$E_{\mathrm{ret}(\mathrm{n}}$,l) for some representative Rydberg levels of Li and Na. We note that storage rings may soon make possible high-precision experiments to determine retardation effects in ions—including helium-like ions such as ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}_{}^{4+}{}_{}{}^{}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}_{}^{6+}{}_{}{}^{}$.

Single- and double-electron capture probabilities of 400–1000-keV ${\mathrm{He}}^{2+}$ projectiles in large-angle scattering on Ar and ${\mathrm{N}}_2$ targets were studied. A classical model for these probabilities, based on the Bohr-Lindhard capture model, was developed for collisions at very small impact parameters with multielectron targets. The model takes into account post-collision relaxation processes when evaluating the double-electron capture probability.