Tracer-diffusion coefficients are presented for several ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$-substituted benzenes of varying molecular weight diffusing in unlabeled benzene at 25°C. The data, which were obtained with one magnetically stirred diaphragm cell, are compared with data in the literature and indicate that a very slight isotope effect is present in this nonpolar liquid.

We have measured the change in the absolute value and the change in the temperature dependence of the elastic coefficients of Ta, as caused by loading with hydrogen. From the results it must be concluded that, in contrast to heavy interstitials like O, N, or C, hydrogen has a long-range strain field with cubic symmetry in spite of tetragonal symmetry of the position.

Dilute alloys of Mn, Co, Ta, and Ir radioisotopes with iron were cooled to 25 mK; the impurity nuclei were oriented through applied magnetic fields up to $H=15.4\mathrm{}$ kOe. At $H\approx 1$ kOe, sufficient to saturate the iron samples, nonalignments of nuclear hyperfine field with $\overrightarrow{\mathrm{H}}$ of magnitude $\Theta \approx 20°$ were observed with $sin\Theta \stackrel{\sim }{\alpha }\frac{1}{H}$. Errors in perturbed-angular-correlation measured $g$ factors (10-40%), nuclear alignment parameters (10-30%), and ultralow-temperature Mössbauer and $\gamma$-ray thermometry (2 mK) due to insufficient $H$ are discussed.

Using a distorted-wave Born-approximation treatment which exactly includes recoil for the data from the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$,${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$ at $E\left({}_{}{}^{14}{}_{}{}^{}\mathrm{N}\right)=78\mathrm{}$ MeV, we demonstrate the necessity for including recoil effects in calculations for single-nucleon-transfer reactions with heavy ions.

The real part of the forward amplitude for Compton scattering on protons was measured through the interference between the Compton and Bethe-Heithler amplitudes by detecting the zero-degree electron pairs asymmetrically. The measurement was made at an average photon energy of $〈k〉=2.2\mathrm{}$ GeV, and an average momentum transfer to the recoil proton $〈t〉=-0.027\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The result confirms the prediction of the Kramers-Kronig relation.

We report a measurement of the missing mass ($\mathrm{MM}$) spectra from the reaction ${\pi }^{-}+p\to {\mathrm{}\left(\mathrm{MM}\right)\mathrm{}}^{-}+p$ at 11, 13.4, and 16 GeV, in the region of the $S\left(1930\right)\mathrm{}$, $T\left(2200\right)\mathrm{}$, and $U\left(2375\right)\mathrm{}$ mesons. Our mass spectra exhibit no narrow enhancements in this region with $〈\frac{d\sigma }{\mathrm{dt}〉}\gtrsim 10$ μb/Ge${\mathrm{V}}^2$.

We present an analysis of 153 events of the reaction $\nu p\to {\mu }^{-}{\pi }^{+}p$ at an average neutrino energy of 1 GeV. The results were obtained using the Argonne 12-ft hydrogen bubble chamber. The reaction is dominated by ${\mu }^{-}{\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$ production for which the total cross section rises from threshold to a value of (0.74±0.18)×${10}^{-38\mathrm{}}$ ${\mathrm{cm}}^2$ at $E_{\nu }\gtrsim 1.0$ GeV. The production and decay angular distributions of the ${\Delta }^{++}$ are given. There is no evidence for hadron-lepton mass enhancements.

New data on the reaction $\nu p\to {\mu }^{-}{\Delta }^{++}$ are compared with theoretical predictions. We stress the importance of the $\Delta$ spin-density matrix in making decisive tests of the models. The data are consistent with the prediction using partially conserved axial-vector currents for $\frac{d\sigma }{d{q}^2}$ near $q^2=0\mathrm{}$. In contrast to previous findings, Adler's relativistic version of the static model is reasonably successful in fitting the data. Zucker's model also fits the data.

We show that elastic unitarity does not require the discontinuities of Regge cuts to vanish at the branch point when the momentum transfer is below the crossed-channel elastic threshold. This is in contrast to the conclusions of Bronzan and Jones.

We show that multiple scattering of the electron (i.e., two-photon exchange) in electron-deuteron elastic scattering leads to a small component in the cross section, which decreases very slowly with momentum transfer and may dominate the cross section at high momentum transfer.

Argon $K$-shell ionization cross sections have been determined from x-ray yields measured in single collisions with beams of the bare nuclei ${\mathrm{C}}^{+6\mathrm{}}$, ${\mathrm{N}}^{+7\mathrm{}}$, ${\mathrm{O}}^{+8\mathrm{}}$, and ${\mathrm{F}}^{+9\mathrm{}}$ at energies of 1.05, 1.50, and 1.88 MeV/amu. The data deviate by as much as a factor of 2.6 from the ${Z_1}^2$ dependence predicted for ionization cross sections. This deviation monotonically increases with $Z_1$ and increases somewhat with velocity.

A nonlocal, energy-dependent, $K^{-}$-nucleus optical potential is derived by means of the independent pair approximation and a $t$-matrix method. Strong coupling of the $K^{-}$-proton pair to the ${Y_0}^{*}$ is taken into account. The effects of nonlocality and off-energy-shell behavior of the $t$ matrix are found to be appreciable. Approximately equivalent local potentials are defined; they all differ significantly from the shape of the nuclear density in the surface region. Shifts and widths of levels in several light kaonic atoms are calculated and found to be in reasonable agreement with experiment.

Highly nonlinear ion acoustic solitons are produced by the superposition of a $15{\lambda }_{\mathrm{D}}$-wide photoionized plasma slab on a dc background. The Mach number increases with the initial step ratio $R$ up to $M\approx 1.95$ for $R\approx 10$. Above $M\approx 1.8$, $R\approx 6$, however, the profiles diffuse rapidly as they propagate. For Mach numbers $M\lesssim 1.8$, a linear interaction is observed in the collision of two solitons traveling in opposite directions, whereas two solitions moving in the same direction exhibit a nonlinear interaction.

A method is described for the direct measurement of the shear-alignment angle in a nematic liquid crystal. Results of such measurements are reported for the nematic phases of three compounds: PAA ($p$, $p^{\prime }$-azoxydianisole), MBBA ($p$-methoxybenzylidene-$p^{\prime }-n$-butylaniline), and HBAB ($p-n$-hexyloxybenzylidene-$p^{\prime }$-aminobenzonitrile). We also report measurements of the rotational viscosity coefficient for the same compounds. In contrast to a recent report by Gähwiller, no orientational instability was found in HBAB.

Rigorous upper and lower bounds are determined for time-dependent correlation functions, of the type used in statistical mechanics and spectroscopy. The input data are the values of any finite number of initial time derivatives of the correlation function. As an example, bounds are found for the classical velocity correlation function for a lattice vibration problem. The bounds are found to be much more accurate than the Taylor series based on the same time derivatives.

New wave-particle processes determining the evolution of large-amplitude, low-frequency ion waves have been observed in numerical and laboratory experiments.

Empirical statistical relationships are found between each of the third moments and the two second moments of solar-wind proton velocity distributions. These can be used to close the Vlasov moment equations when applied to the behavior of the solar-wind plasma over a sufficiently large temporal or spatial scale.

Cyclotron phase resonance (CPR) is observed at 116 GHz in sodium and potassium. The CPR signal shows effects due to electron correlations, including notches in the transmission amplitude, an asymmetry, and possibly a shift in resonance field from the Azbel-Kaner cyclotron-resonance (AKCR) value. A simple model describing these effects appears to indicate that CPR is a $k=0\mathrm{}$ resonance in the conductivity, i.e., a uniform resonance whose shift from AKCR should give the Fermi-liquid parameter $A_1$. Values found for $A_1$, however, disagree with previous estimates.

The exchange energy is found for electrons in a two-dimensional system and in Si inversion layers which are dynamically two dimensional. We find that exchange lowers the energy of the lowest sub-band in Si inversion layers significantly, but affects the energies of higher sub-bands and the spatial extent of the wave functions in the direction perpendicular to the surface only slightly.

An x-ray photoemission study of evaporated Al films has been performed in ultrahigh vacuum. The striking similarity of the valence-band spectrum with computed density of states allows a straightforward interpretation of the results. Core level spectra reveal structures which can be attributed to either inelastically scattered electrons or to satellites due to hole-plasmon coupling.