A theory of the Poisson Green’s function is given for the case of an interior region of dielectric constant ${\epsilon }_i$ separated by an arbitrary closed interface from an exterior region of dielectric constant ${\epsilon }_e$. A convergent multiple induction expansion is developed as the basis of an approximation scheme for the Green’s function. In a sense, this expansion effectively extends the method of images to surfaces of arbitrary shape. As an application of the general theory, a protein in an aqueous electrolyte is modeled as a charge-bearing region of low dielectric constant surrounded by a region of high dielectric constant.

Let ψ be any normalizable energy eigenfunction for N electrons in an atom having Z protons in a fixed pointlike nucleus. Recently, it has been shown with use of quantum mechanics [Phys. Rev. Lett. 53, 907 (1984)] that, for the state ψ, NF no larger than 4. Evidence was presented that F=F(N)→2 as N→∞. In this paper we show that the same result holds in classical mechanics for a bound system.

Calculations of the energy distribution of electrons ejected in ion-atom collisions have been performed by representing continuum wave functions in terms of pseudostates. It is illustrated that for proton-hydrogen collisions the electron spectrum in the low-energy region is in good agreement with that calculated by the use of exact continuum wave functions. In the case of ionization of helium by proton impact, the present results are compared with experimental data as well as with Born Hartree-Fock calculations.

Opportunities to study the strong asymmetry between target-atom ionization by charged projectiles vis a vis projectile ionization by neutral target atoms are afforded by the relatively new technique of zero-degree Auger-electron coincidence spectroscopy. Examples of the asymmetry in the degree of outer-shell stripping observed are noted, and recent theoretical work contrasting the n dependence of the ionization of hydrogenic systems when struck by charged vs neutral particles is mentioned.

The conventional minimum principle for single-channel scattering is modified to eliminate the requirement that the static part of the open-channel problem must be solved exactly in order to maintain the bound property. The new formulation is easier to apply, at the expense of a slight compromise in the rigor of extremum property.

Cross sections for the production of positive ions and electrons and for the capture and loss of electrons by 5–450-keV ${\mathrm{He}}^{+}$ ions making collisions with water-vapor molecules have been measured. The ionization cross sections ${\sigma }_{+}$ and ${\sigma }_{\mathrm{-}}$ were measured by the transverse-field method and the electron-capture and -loss cross sections ${\sigma }_{10}$ and ${\sigma }_{12}$ by electrostatic separation of the beam components after passing through a known length of target gas. The four cross sections were adjusted to satisfy the equation ${\sigma }_{+}$-${\sigma }_{\mathrm{-}}$=${\sigma }_{10}$-${\sigma }_{12}$. .AE

The two-photon-annihilation rates for some ${}_{}{}^1{}_{}{}^{}\mathrm{S}_{}^{\mathrm{e}}{}_{}{}^{}$ doubly excited states of positronium negative ions are calculated. Hylleraas-type wave functions are used to represent the system. The doubly excited wave functions are obtained by use of a stabilization method. In comparing the annihilation lifetimes with the autoionization lifetimes (related to the inverse of the resonance widths that were obtained previously by using the method of complex-coordinate rotation), it is concluded that the decay mode of these lower-lying doubly excited ${}_{}{}^1{}_{}{}^{}\mathrm{S}_{}^{\mathrm{e}}{}_{}{}^{}$ states is dominated by autoionization processes.

An approximate theory is presented for the propagation of an ionizing light pulse through a gaseous medium. Saturation occurs in the pulse attenuation as the ground-state population is depleted.

We consider the critical dynamics of the smectic-C to -A transition in freely suspended thin films. Close to the transition the films can be considered literally two-dimensional, and at sufficiently long wavelengths, the system should be equivalent to a two-dimensional XY model. The dynamics of this system are very similar to those of the hexatic-to-isotropic melting previously studied by Zippelius, Halperin, and Nelson [Phys. Rev. B 22, 2514 (1980)]. However, the order parameter in the smectic films is considerably easier to probe experimentally. We discuss the experimental predictions of the present theory and suggest possible experiments.

The authors address the problem of quantum Brownian motion at low temperatures and with arbitrarily strong damping. For a harmonically bound particle the zero-temperature correlation functions are shown to display long-time tails. At finite temperatures an power-law decay at intermediate times is followed by an exponential decay with time constant ħ/2π$k_B$T. The case of free Brownian motion is treated, and some general conclusions for nonlinear systems are drawn.

Global features of chaos observed after an initial period-doubling route to chaos in a driven p-n junction oscillator are found to result from a simple mechanism which consists of a driven linear oscillator reset by a relaxation oscillator. The global features include staircases, period adding, replication, hopping, and higher-order periodic windows. A one-dimensional iterative map is constructed which models the initial quadratic behavior and subsequent global behavior. Other systems where this mechanism may be found are discussed.

By the method of maximization of entropy a consistent kinetic theory is derived for a square-well fluid. The existence of an H theorem is shown, and the equilibrium solutions are constructed.

The dielectric behavior of hydrated di-myristoyl-phosphatitylcholine (DMPO) bilayers was investigated as a function of temperature at frequencies from 4 to 12 GHz. A steplike increase of the dielectric constant occurs at the chain melting phase transition. It is related to a dielectric dispersion due to the onset of the acyl-chain isomerization rotation. The measured dielectric response, with its unexpectedly high values, is interpreted as a cooperative rotational motion within larger chain clusters. A lower limit for the cluster size of at least 250 ${\mathrm{CH}}_2$—${\mathrm{CH}}_2$ bonds with correlated rotation is deduced.

It is shown that local-field effects in the neutron optical potential produce a nonvanishing Fizeau effect and that the magnitude of the effect is particularly large for cold neutrons with wavelengths λ≳13 Å. .AE

The internal consistency of the procedure described by Brey, Santos, and Rull [Phys. Rev. A 26, 2993 (1982)] to determine the thermodynamical properties of the Lennard-Jones classical fluid in the critical region on the basis of the Percus-Yevick (PY) equation is discussed and found inadequate. New results for the solution of this equation near the critical point for a much larger range in r space are presented. We consider the sum of two Yukawa potentials as the pair interaction. Our results are in complete agreement with the critical behavior found with models exactly soluble (adhesive hard spheres and lattice gas) in the PY approximation: classical critical exponents but a nonclassical scaling function that leads to an asymmetry between liquid and vapor with a true spinode present only for ρ>${\rho }_c$.

The experiments of Gibson and Jeffries on ferromagnetic resonance at very high signal powers are simulated with a model involving coupling of only one spin wave to the uniform mode. Bifurcation sequences and chaos similar to the ones observed are found in the computation.

We have performed calculations of the spin asymmetry in elastic scattering of electrons by hydrogen atoms using an optical potential appraoch. An 18-state basis set is employed. The scattering calculations are carried out explicitly for the channels corresponding to the lowest six states. The effects of other channels are included via a second-order optical potential. The present values of the asymmetry at 90° are in agreement with the recent experimental values of Fletcher et al. and resolve the discrepancy between theory and experiment which they reported in the intermediate-energy region.

We report a perturbative calculation of the cross sections for two-photon free-free transitions (absorption and emission) in a Coulomb potential within the nonrelativistic, dipole approximation. The matrix element was integrated analytically by the Green’s-function method, and then computed numerically with great accuracy. Limiting cases are discussed (Born approximation, low and high photon-electron energy ratios). Results are presented for two-photon absorption, in the case when the initial electron momentum is perpendicular to the photon polarization vector.

It has been observed experimentally that total ionization cross sections for neutral atoms exhibit abrupt increases near thresholds for exciting inner-shell electrons to autoionizing states. This feature of the ionization cross section is not predicted by most of the standard first-order theories. While a recent R-matrix calculation produced cross sections of the type observed experimentally, the physical effects contributing to the structure were not apparent. We have studied this effect in the distorted-wave approximation and have found that the rapid increase in the ionization cross section near autoionization thresholds results from exchange effects. Calculated angular distributions for Li, where this mechanism operates, are dominated at backward-scattering angles, a feature amenable to experimental observation.

The magnetic quantum number selection rule implies that radiation that is linearly polarized perpendicular to the electric field will not excite Δm=0 transitions. This phenomenon in Stark spectra has been used to determine the electric field vector in a positive column dc discharge in helium. The technique is applicable to both linear and nonlinear Stark effects.