We report high-resolution differential cross sections at thermal energy for polarized, rotationally state-selected LiF on Ar. They were 2-8% larger with LiF in the $J=\left|M\right|=1\mathrm{}$ orientation along the relative velocity than in the $J=1\mathrm{}$ unpolarized state. The differential cross section in the present case is much more sensitive to change in polarization than is the total cross section. The high-frequency oscillations of the differential cross sections were found substantially independent of $J$ when the present $J=1\mathrm{}$ data were compared with non-state-selected data for $\overline{J}=15\mathrm{}$ or $\overline{J}=25\mathrm{}$.

We report the continuous growth, on a microscopic scale, of solid ${\mathrm{He}}^4$ from superfluid ${\mathrm{He}}^4$ caused by its substrate interaction with Grafoil. The measurements indicate the presence of a surface solid layer whose thickness varies from 8 Å to more than 30 Å from the Grafoil substrate as the bulk solidification curve is approached. The results are in good agreement with a theory based on the van der Waals attraction between the ${\mathrm{He}}^4$ and the substrate.

We show that by using a simple optical method, thermodiffusion processes can be exploited for an accurate, reasonably fast determination of the diffusion coefficient $D$ for various macromolecules in solution. As a byproduct, reliable values for the thermal-diffusion ratio $k_T$ are also derived. Furthermore, we report experimental evidence of a new type of convective instability generated in a dilute solution of macromolecules heated from above.

It is shown that zero-point and thermal vibrations change the vacancy formation volume calculated from classical lattice statistics by usually no more than ${10}^{-3\mathrm{}}$ at all temperatures. In view of the recent interest in relating the temperature variation of the vacancy formation volume to Arrhenius plot curvature, the validity of lattice statics, as a tool for the calculation of temperature-dependent defect properties, is established.

The trigonal-to-pseudotetragonal structural first-order transition in [111]-stressed SrTi${\mathrm{O}}_3$ is shown to be a realization of the continuous three-state Potts model. The measured order-parameter discontinuity at the transition, $〈\Delta \overrightarrow{\varphi }〉$, depends on the trigonal order parameter $〈{\varphi }_{\mathrm{}\left[111\right]\mathrm{}}〉\propto M$ as $\left|〈\Delta \overrightarrow{\varphi }〉\right|\propto {\mathrm{}\left|M\right|\mathrm{}}^{{\delta }^{*}}$, with ${\delta }^{*}=0.62\mathrm{}\pm 0.10$ (mean-field theory predicts ${\delta }^{*}=1\mathrm{}$). This agrees with renormalization-group predictions, and proves that the model has a first-order transition even in the fluctuation-dominated region.

Incident electrons follow a parabolic trajectory when an electric field is applied normal to the surface of a metal crystal with force vector directed outwards. Under appropriate conditions touching trajectories may be neglected, and electron-surface-plasmon scattering is dominated by trajectories with closest approach distance. Experimental results are presented for Mo indicating that only the 1.3-eV molybdenum surface plasmon is excited. Application of this new technique to measurements such as surface-plasmon dispersion is outlined.

A novel, double-beam photoemission experiment is described in which electron energy distributions are obtained from semiconductors by modulating the ultraviolet photocurrent with a tunable, flash-excited, dye-laser beam. Double-beam photoemission spectra are demonstrated, in the case of tellurium, to result from optical transitions alone within the unperturbed bulk band structure of the solid. Unique information is obtained on the conduction-band-states distribution below vacuum level, within which a forbidden gap is demonstrated to exist between 2.5 and 4.7 eV above valence-band edge.

By considering the results of Mössbauer studies and x-ray photoelectron spectroscopy, we obtain a phenomenological model of the intermediate valence state in the homogeneous system Eu${\mathrm{Rh}}_2$. The interconfiguration excitation energy is 1550 ± 150 K, and the mixing width, $2\Delta$, is 0.10 ± 0.02 eV. In $\mathrm{Eu}{\mathrm{Rh}}_{2-x}{\mathrm{Pt}}_x$ the Eu valence is determined by the local environment, including neighbors beyond the nearest shell.

In this paper we describe the principles of a new, nondestructive method of determination of the potential distribution in delectrics. It is shown that a pressure discontinuity propagated in a sample acts as a virtual probe sensitive to potentials. The time dependence of such externally measurable parameters as voltages or charges on the electrodes is thus a direct image of the inner potential distribution which existed in the sample before the introduction of the perturbation.

We report a measurement of the frequency spectrum of x-ray transition radiation. X rays were generated by electrons of 5 and 9 GeV in radiators of multiple polypropylene foils, and detected in the range 4 to 30 keV with a calibrated single-crystal Bragg spectrometer. The experimental results closely reproduce the features of the theoretically predicted spectrum. In particular, the pronounced interference pattern of multifoil radiators and the expected hardening of the radiation with increasing foil thickness are clearly observed. The overall intensity of the radiation is somewhat lower than predicted by calculations.

The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}(\gamma , p_0)$ cross section has been measured for a series of photon energies between 100 and 300 MeV at proton angles of 45°, 90°, and 135°. Above 250 MeV, the results exceed simple shell-model predictions by several orders of magnitude. The data are compared with a calculation which involves $\Delta$ excitation in an intermediate state.

Evidence is presented for local compensation of transverse momentum in $\mathrm{pp}$ collisions at 200 and 300 GeV/c. We compare the data with a model which contains no dynamical transverse-momentum correlations. These data are used to determine a lower bound on the slope of the Pomeranchuk trajectory.

The pion-absorption contribution to the $\pi$-$d$ scattering length ($a_{\pi d}^{}{}_{}{}^{\prime }$) is calculated in the Hulthén model in a simple dispersion-theoretic approach with Koltun-Reitan input modified through the introduction of the off-shell $S$-wave range parameter ${\alpha }_0$ with ${\alpha }_0=500\mathrm{}$ MeV/c. In this approach one finds the uncrossed result, $a_{\pi d}^{}{}_{}{}^{\prime }=-2.69\mathrm{}\times {10}^{-3\mathrm{}}m_{\pi }^{}{}_{}{}^{-1\mathrm{}}$, increased by $1.30\times {10}^{-3\mathrm{}}m_{\pi }^{}{}_{}{}^{-1\mathrm{}}$ with the inclusion of crossing.

Inelastic differential cross sections have been measured for ${\pi }^{\pm }p$, $K^{\pm }p$, and $p^{\pm }p$ at 140- and 175-GeV/c incident momentum over a $\mathrm{}\left|t\right|\mathrm{}$ range from 0.05 to 0.6 ${\mathrm{GeV}}^2$ and covering a missing-mass region from 2.4 to 9 ${\mathrm{GeV}}^2$. For $M_x^{}{}_{}{}^2$ greater than 4 ${\mathrm{GeV}}^2$, the invariant quantity $\frac{M_x^{}{}_{}{}^2{d}^2\sigma }{\mathrm{dt}dM_x^{}{}_{}{}^2}$ was found to be independent of $M_x^{}{}_{}{}^2$ at fixed $t$ and could be adequately described by a simple triple-Pomeron form. The values obtained for the triple-Pomeron couplings are identical within statistics for all channels.

We have made the first measurement of the spin-spin correlation parameter $C_{\mathrm{SS}}$ in $\mathrm{pp}$ elastic scattering at 6 GeV/c over the $\mathrm{}\left|t\right|\mathrm{}$ range from 0.05 to 1.5 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The measured $C_{\mathrm{SS}}$ data points are all negative, and their absolute values increase with $\mathrm{}\left|t\right|\mathrm{}$. The results are compared with some existing attempts to describe the $\mathrm{pp}$ scattering process.

The invariant cross section for the inclusive production of ${\pi }^{+}$, ${\pi }^{-}$, $K^{+}$, $K^{-}$, $p$, and $\overline{p}$ is presented for proton-nucleon interactions at $p_{\mathrm{lab}}=28.5\mathrm{}$ GeV/c. Beryllium, titanium, and tungsten targets were used and the yields were extrapolated to $A=1\mathrm{}$ using the power law $\sigma \sim A^{\alpha }$. The exponent $\alpha$ increases with $p_T$, except for protons. The $p_T$ dependence of the cross sections is compared with a simple fireball model.

Two samples of Madagascar monazite from the same geological formation as the biotite studied by Gentry et al. were examined by using a neutron multiplicity counter capable of detecting binary or ternary spontaneous fission decay in any element. No events characteristic of spontaneous fission decay of superheavy elements were found. Derived limits indicate that if superheavy elements were present, then their spontaneous fission halflives must be extremely long or their concentrations extremely small.

The cranking model is applied to a two-center, asymmetric, shell model plus a pairing interaction. The energy increase due to the enforced collective motion is determined up to fourth order in the collective velocity. For a motion across the second saddle of ${}_{}{}^{236}{}_{}{}^{}\mathrm{U}$ the higher order terms are so large that the validity of the adiabatic model as a first approximation to fission dynamics is questionable.

We have found that tantalum $K$ x rays resulting from the $K$ capture of ${}_{}{}^{181}{}_{}{}^{}\mathrm{W}$ to ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ are lower in energy than the "normal" Ta $K$ x rays produced by self-fluorescence in a tantalum source. The resulting shift, $E_{\mathrm{W}\mathrm{ }\mathrm{source}}-E_{\mathrm{Ta}\mathrm{ }\mathrm{source}}=-0.67\mathrm{}\left(13\right),-0.96\mathrm{}\left(12\right),-1.8\mathrm{}\left(5\right)\mathrm{}$ eV for the Ta $K{\alpha }_1$, $K{\alpha }_2$, and $K{\beta }_1$ lines, respectively. An interpretation in terms of a multiple-electron shake-off is presented.

Self-focusing of spatially nonuniform coherent pulses has been seen in the center of Na and Ne transitions. Self-focusing and temporal reshaping were studied as a function of laser detuning in Na. The dependence of on-resonance self-focusing upon input pulse area was observed in Ne. Numerical solutions of the Maxwell-Bloch equations including transverse variations predict coherent self-focusing and yield a single parameter for estimating its importance for a given beam diameter and sample absorption.