The He-Ne potential is obtained from the measured differential cross section by a systematic inversion procedure based on the generalized opitcal theorem. The potential, obtained in the range from 2.1 to 6 Å, is in good agreement with recently proposed model potentials. The results constitute the first example of a fully direct and systematic inversion of experimental scattering data of real systems.

The drift velocity of electrons in helium gas at low temperatures is found to exhibit an anomalous dependence on density, similar to that which has been observed at much higher temperatures. The density and temperature dependence of the effect suggests that it arises from multiple-scattering corrections to the classical transport behavior. The effect may account for some of the phenomena which have previously been ascribed to electron localization.

An analytic theory for the expansion of a laser-produced plasma with two electron temperatures is presented. It is shown that from the ion-emission velocity spectrum such relevant parameters as the hot- to cold-electron density ratio, the absolute hot- and cold-electron temperatures, and a sensitive measure of the hot- to cold-electron temperature ratio can be deduced. A comparison with experimental results is presented.

A kinetic analysis of magnetohydrodynamic ballooning modes has been carried out in the limit of large toroidal mode numbers. At marginal stability, the mode acquires a real frequency. The finite ion Larmor radius and perturbed electron pressure anisotropy are stabilizing effects, whereas the perturbed ion pressure anisotropy and the longitudinal electric field are destabilizing. By minimizing the stability effect and maximizing the destabilizing effect, the critical $\beta$ may be 10% lower than that predicted by the magneto-hydrodynamic theory.

It is shown that the $B$ phase not only has a "phase dynamics" such as that in He II, but also an orbital dynamics somewhat similar to that of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ or a nematic liquid cyrstal. The rederived $B$-phase hydrodynamic theory, complete with nonlinear terms, establishes the equivalence between rotations in orbital and spin spaces and shows the intriguing possibilities of generating a magnetization by mechanical rotations and of substituting the magnetic field with oscillating parallel plates in "NMR" experiments.

An extensive satellite peak structure in the attenuation of 5-MHz zero sound is observed and characterized in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$. The satellites, not predicted by theory, have a strong pressure dependence and are most closely spaced and narrowest near zero pressure.

NMR has been used to study the orientational behavior of registered lattices of ortho-${\mathrm{H}}_2$ and para-${\mathrm{D}}_2$ molecules adsorbed on graphite in the range 1.3-4.2 K. The results show a weak crystal field (0.56 K for $o$-${\mathrm{H}}_2$ and 2.4 K for $p$-${\mathrm{D}}_2$). In addition, $p$-${\mathrm{D}}_2$ molecules experience a temperature-dependent molecular field arising from electrostatic quadrupole-quadrupole interactions. No orientational ordering occurs down to 1.3 K, a factor of 2 below the mean-field transition temperature.

We have observed a sharp threshold for the process of optically induced glide at which the velocity changes by more than a factor of ${10}^3$ when the excitation intensity changes only 20%. This threshold is insensitive to doping and to the presence of a $p-n$ junction. The effect is shown not to be related to recombination-enhanced motion or to local heating. An explanation in terms of the reduction of frictional forces by interaction with unrecombined carriers is offered.

Ni, Co, and Fe films of a few atomic layers are condensed in UHV at 10 K on metallic substrates. Anomalous-Hall-effect measurements are used to determine the magnetization and the susceptibility of the films. Ni films with a thickness smaller than two atomic layers possess no magnetic moment but show an enhanced susceptibility. Between two and three atomic layers of Ni the susceptibility diverges and thicker films possess a magnetic moment. For Co and Fe, the first monolayers already shows a magnetic moment.

Exciton dynamics in Mn${\mathrm{F}}_2$ are investigated using time-resolved laser spectroscopy. At 1.7 K the decay of the intrinsic $E1\mathrm{}$ exciton is nonexponential, independent of the particular traps present, and strongly dependent on pump intensity. We show that a biexciton decay model describes the qualitative behavior of the system and fits the decay data quantitatively over three decades. Values for the transfer rate to traps and the biexciton decay rate are also obtained.

It is shown that $m_u=0\mathrm{}$ does not lead to numerical disagreements and that it implies an improvement of the SU(2) ⊗ SU(2) symmetry.

In $e^{+}{e}^{-}\to \mathrm{hadrons}$ an azimuthal angular correlation between a plane defined by the hadrons and the plane formed by the beams and the jet axis is possible. In the naive parton model the correlation vanishes. In quantum chromodynamics it does not and with reasonable assumptions may be reliably calculated in perturbation theory for large center-of-mass energy. We calculate it in lowest nontrivial order and discuss its physical origins and experimental observation.

The parity-nonconserving circular polarization of $\gamma$ rays from the 2.789 → 0.0 MeV transition in ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ is found to be (-9 ± 51) × ${10}^{-4\mathrm{}}$, which corresponds to a parity-mixing matrix element $\left|〈H_{\mathrm{PNC}}〉\right|=0.009\mathrm{}\pm 0.054$ eV between the 2.80-MeV, $J^{\pi }={\frac{1}{2}}^{\pm }$ levels. This value is considerably smaller than the measured parity mixing in the $J=\frac{1}{2}$ doublet in ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$.

This paper reports measurements of the analyzing power, $A_y$, in the production of both "backward" protons and forward (quasifree scattering) protons in the reaction $p+A\to p+X$, using 800-MeV polarized protons. For the backward protons the measurements show large negative $A$-dependent values of $A_y$ at low momenta, changing to large positive values at high momenta; in the quasielastic region, $A_y$ is large and positive, is smaller than $A_y$ measured in hydrogen, and decreases with increasing $A$.

$p$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ elastic scattering has been measured at 1.05-GeV incident proton energy, close to 180° in the center of mass. The steep backward peak observed at lower energies is still present, but its slope appears to decrease.

The $N_{4,5}{O}_{2,3}{O}_{2,3}$ Auger spectra from Xe and the $M_{4,5}{N}_{2,3}{N}_{2,3}$ Auger spectra from Kr are investigated for different photon energies around threshold ionization. When exciting at the resonance line ($4d^{9}5s^{2}5p^{6}6p$ for Xe and $3d^{9}4s^{2}4p^{6}5p$ for Kr) we observe the usual Auger multiplet structure to be shifted to higher kinetic energies. Additionally, new lines appear which can be assigned to shake-up processes in the ${\mathrm{Xe}}^{+}$ and ${\mathrm{Kr}}^{+}$ ions.

We present angle and energy distributions of H atoms emerging from thin carbon foils bombarded with MeV ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_3^{+}$ beams. If the target is thin enough, a projectile electron can participate in the formation of a neutral atom at emergence through dissociation of a vibrationally excited ${\mathrm{H}}_2^{+}$ molecule. This process is not observable with thicker targets when the formation of a neutral requires the capture of a target electron. The results suggest that electrons can be bound to the projectile inside the solid.

Theoretical calculations, confirmed by experimental measurements, are used to obtain a new scaling rule for electron loss from a hydrogen atom in collision with a heavy, highly stripped ion. The calculations cover the energy range 50 to 5000 keV/amu and charge states $q$ from 1 to 50. The experiments are in the range 108 to 1140 keV/amu and charge states 3 to 22. A simple analytic expression that describes the electron-loss cross section for $1<~q<~50$ in the energy range 50 to 5000 keV/amu is presented.

The TRISO PS III machine at the University of Miami has been modified by improving the preionization of the plasma and increasing the ring frequency of the conical $\theta$-pinch coils. The secondary magnetic compression field has been increased to 120 000 G at the conjugate points of the mirror. It has been possible, with this modified machine, TRISO PS IV, to obtain ion temperatures of 5 keV with corresponding electron temperature of less than 300 eV. The electron density was 2×${10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$. This plasma was held in stable equilibrium for 5 μsec.

Observations of stimulated Raman backscatter in an underdense hydrogen plasma are reported. The wavelength shift associated with the backscattered Raman component is consistent with a plasma with the measured electron density. The Raman backscatter is seen to decrease below detectable levels when the incident C${\mathrm{O}}_2$-laser intensity is attenuated approximately 50%, consistent with theoretical intensity thresholds of the Raman process.