We present calculations for the impact-parameter dependence of K-shell ionization rates in p¯-Cu and in p¯-Ag collisions at various projectile energies. We show that the effect of the attractive Coulomb potential on the Rutherford trajectory and the antibinding effect caused by the negative charge of the antiproton result in a considerable increase of the ionization probability. Total ionization cross sections for proton and antiproton projectiles are compared with each other and with experimental ionization cross sections for protons.

The contributions of higher partial waves to the elastic scattering amplitude are dominated by long-range interactions which fall off as $r^{\mathrm{-}n}$ as r→∞. Closed-form expressions for the contributions of higher partial waves (2l>n-3) to the scattering amplitude for various long-range interactions (n ranging from 3 to 8) are presented.

Relativistic electrons in tenuous media moving parallel to an external magnetic field show a complex radiation pattern. The emission of Čerenkov radiation may even induce transitions into higher excited Landau levels of the electron if certain kinematical conditions are met. The respective rates are evaluated and it is found that at higher frequencies the spectrum is strongly suppressed as compared with ordinary Čerenkov radiation.

We consider the propagation of electromagnetic radiation through a medium consisting of noninteracting harmonically bound electrons in a blackbody-radiation heat bath. An exact result for the ac conductivity is obtained, which differs from the well-known Drude-Lorentz result by the presence of memory (non-Markovian) effects. In particular, the absorption line is considerably changed in shape, especially away from resonance. Our approach—which is based on the use of a generalized quantum Langevin equation—transcends the particular model discussed as it enables the conductivity to be calculated directly, in contrast to Kubo-type calculations which require the evaluation of correlation functions as an intermediate step. Furthermore, the model itself should prove useful as a testing ground for the various quantum theories of conductivity which are presently being explored for possible use in studies of submicron semiconductor devices.

The formula for the asymptotic degree of radiative polarization in a high-energy storage ring (the Derbenev-Kondratenko formula) was recently rederived and extended to first order in g-2. Here the formula is generalized to all values of g.

An experimental study of laser-induced collisional energy transfer in a mixture of europium and strontium vapors is reported. The profile of the excitation spectrum in the static wing has been measured with high accuracy and compared with available calculations, demonstrating that simple two-level models are inadequate to describe the transfer process. A comparison with the predictions of a three-level model assuming dipole-dipole interaction, recently developed by Bambini and Berman, shows for the first time agreement between theory and experiment.

Some halides and hydroxides containing either potassium, rubidium, or cesium have been bombarded with 80-keV ${\mathrm{Ar}}^{+}$ ions. The light emitted from sputtered particles has been studied in the wavelength range 200–900 nm. In each case some spectral lines, which cannot be identified as previously observed transitions, have been seen. They are tentatively classified as transitions among core-excited levels in the neutral potassium, rubidium, or cesium atoms. A discussion of possible assignments is given.

A simple technique for producing a single-state sodium atomic beam is described. A single laser both optically pumps the F=2 ground-state atoms into $m_F$=+2 and deflects the pumped atoms away from residual F=1 atoms. Data demonstrating the technique are presented, and a practical design for an apparatus based on these principles is described.

The effect of laser linewidth associated with the phase fluctuations on the photon statistics in a degenerate parametric process is studied.

Using a generalized Landau type of free-energy density, we develop a theoretical model which, in a unified way, describes the general features of the tilt, polarization, pitch, dielectric susceptibility, and heat capacity of ferroelectric liquid crystals. Rewriting the equations into dimensionless form, we show that six parameters are needed in order to account properly for the temperature dependence of the quantities in question. It is also shown that the introduction of a biquadratic coupling between the tilt and the polarization in the free-energy density, which is an essential part of the model, implies a crossover behavior of the polarization when plotted as a function of temperature.

A prototype driven nonlinear two-dimensional oscillator with a limit cycle is studied. Three parameters α, β, and γ characterize the dynamics: the amplitude α of the external force, the frequency ratio β between the drive and the natural period, and the relaxation rate γ for perturbations off the limit cycle. Several limiting cases can be investigated analytically. The claim that this model is representative of a wide class of nonlinear oscillators is substantiated by showing that appropriate two-dimensional cross sections of the parameter space are qualitatively similar to known special cases.

The postponement of Hopf bifurcations driven by a swept bifurcation parameter is demonstrated with an electronic Brusselator. Noise on the swept parameter destroys the postponement and the bifurcation as it is usually defined.

Observation of the type-II Pomeau-Manneville intermittency was realized in a coupled nonlinear oscillator circuit employing a p-n junction diode and linear oscillator elements. It seems that Hopf bifurcation and period tripling are among the most important precursors to the type-II intermittency. Experimental results are found to agree very well with the numerical results derived from the coupled discrete maps of Pomeau-Manneville.

A closed-form formula is given for the mean power radiated per solid angle in a given direction by a relativistic particle in cyclotronic motion with a nonzero parallel velocity. The difference between emitted and received mean power for a nonclosed periodic motion is illustrated in this case.

A new method, based on the eigenvalue problem of the master equation of discrete dynamical systems, is applied to the calculation of the escape rate from chaotic repellers or semiattractors. The corresponding eigenfunction is found to be smooth along unstable directions and to be, in general, a fractal measure. Examples of one- and two-dimensional maps are investigated.

We consider randomly linked polymer chains (polymeric fractals) in solution, where the size of the solvent objects is the relevant parameter. The solvent can be of small molecules, or of the size of the fractal itself. As long as the size of the solvent is small compared to the polymeric fractal, ordinary swelling appears. If all polymers are of the same size, the swelling behavior and the upper critical dimensions are different. Such questions are of relevance in gelation.