X-ray scattering studies in single-crystal beryllium reveal for the first time an anisotropy in both the plasmon dispersion and linewidth. By comparing the data with random-phase-approximation-type theory which includes band structure, we can begin to separate the contributions from the lattice and from the true many-body interactions to the temporally and spatially dependent response of an interacting electron gas at metallic densities.

We report here evidence for the first paraferroelectric transition observed in a pure molecular solid (without H bonds); we present results from x-ray diffraction, calorimetric and dielectric measurements, and direct optical observation of domain-wall displacement under an applied electric field.

A new degree of freedom associated with shifting of particles between the even-parity-orbitals system and the odd-parity-orbitals system is introduced in the study of the nuclear rotational problem. It is found that this new mode contributes significantly to the deviation from the $I(I+1\mathrm{})\mathrm{}$ rule, with correction terms comparable to the Coriolis antipairing effect.

The reaction ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$(${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{49}{}_{}{}^{}\mathrm{Sc}$ has been investigated at 50 MeV using a magnetic spectrometer. Angular distributions were extracted for 16 levels below 5.8 MeV excitation. The relative yields of levels were found to be similar to (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $d$). The ground-state angular distribution (transferred $L=4\mathrm{}$) peaked at the most forward angle observed (9° c.m.), but the yields of other strong levels ($L<~2$) did not. This apparent $L$-dependence was reproduced by no-recoil distorted-wave Born-approximation calculations using weakly absorbing potentials.

The $\alpha$-decay energies and half-lives of three new thorium isotopes, ${}_{}{}^{218-220}{}_{}{}^{}\mathrm{Th}$, have been measured by a simple recoil technique. The observed $\alpha$-decay widths are in qualitative agreement with Mang's shell-model theory.

A calibrated detector of kilohertz-band gravitational radiation has been built which has sufficiently improved sensitivity over Weber's apparatus to allow comparison with his two-detector coincidence results. No events were observed by us at 710 Hz during a recent three-month period of observation. Weber's data at 1661 and 1030 Hz would imply that we should have seen more than 400 events. During these observations, our sensitivity to gravitational bursts was many times that of Weber during 1969-1970. Absolute limiting flux values are given.

Using available experimental data, we give an upper bound for the sum of ${\sigma }_{\mathrm{tot}}\left({\pi }^{+}p\right)$ and ${\sigma }_{\mathrm{tot}}\left({\pi }^{-}p\right)$ above 60 GeV. It rules out an appreciable increase of this sum beyond 60 GeV.

The spin and parity analysis of the ${\eta }^{\prime }\mathrm{}\left(958\right)\mathrm{}$ from the distribution of events on the ${\pi }^{+}{\pi }^{-}\eta$ and the ${\pi }^{+}{\pi }^{-}\gamma$ Dalitz plots has been shown to favor $J^P=0^{-}$ over $2^{-}$, but not conclusively. The Brookhaven National Laboratory-University of Michigan data reported here indicate anisotropies in the production and decay correlation angular distributions. Earlier Lawrence Berkeley Laboratory data dilute these effects. The observed anisotropies weaken the evidence for a $J^P=0^{-}$ assignment for the ${\eta }^{\prime }\mathrm{}\left(958\right)\mathrm{}$.

A Dalitz plot of $1.6\times {10}^6{K_L}^0\to \pi \mu \nu$ decays has been studied to measure the $t$ dependence of the vector and scalar form factors. The observed slopes, ${\lambda }_{+}=0.030\mathrm{}\pm 0.003$ and ${\lambda }_0=0.020\mathrm{}\pm 0.003$, are compatible with current-algebra and soft-pion predictions, $\mu -e$ university, and $K^{*}$ (890) dominance of the vector form factor.

We have observed the oscillatory magnetic-field and time dependence of the fluorescence from the ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ levels of Ba and Ca excited by a pulsed tunable dye laser. We have observed level-crossing signals narrowed by the technique of time-delayed observation.

Proton energy spectra have been obtained from the dissociative ionization of ${\mathrm{H}}_2$ by electrons which reveal the existence of many new states lying between the $1s{\sigma }_{\mathrm{g}}$ ground state of ${\mathrm{H}}_2^{+}$ and the $2p{\sigma }_{\mathrm{u}}$ repulsive state.

It is shown that the stipulation of lossless propagation provides sufficient asymptotic information on the pulse-propagation process to permit determination of both amplitude and phase of a class of coherent optical pulses ($2n\pi$ pulses, $n=0, 1, 2, \dots$) by the inverse method. Results for $n=1\mathrm{} \mathrm{and} 2$ are summarized.

We report intense stochastic ion heating comparable to the electron heating, proportional to the energy density of the fluctuating electric fields of the ion-acoustic component of the decay instability. The ion-temperature rise time is comparable to, but longer than, the instability growth time, and many orders of magnitude shorter than collisional relaxation times.

We have obtained conditions for excitation of parametric instabilities in bounded plasmas. Damping and inhomogeneity effects are taken into account. The results are found to be of special importance for backscatter Brillouin instability.

Nonequilibrium molecular dynamic simulation of liquid argon yields the strain-rate dependence of shear viscosity. Near the triple point the apparent viscosity decreases with increasing strain rate; the extrapolated zero-gradient viscosity is consistent with the equilibrium Green-Kubo viscosity calculated by Levesque, Verlet, and Kurkijarvi. At higher temperatures along the saturated vapor pressure line, our results are insensitive to the strain rate and agree well with experimental data for liquid argon.

The persistent velocity autocorrelation, first discovered by Alder and Wainwright through molecular dynamic computations, is confirmed experimentally in gaseous air and argon for the first time. Analysis is based on hydrodynamic considerations.

Finite-amplitude plasma waves excited by plates outside a plasma column are shown to decay into other plasma waves and electrostatic ion cyclotron waves, accompanied by ion heating.

Thin-film aluminum superconducting tunnel junctions can be used to generate phonons up to ${10}^{12}$ Hz. This is substantiated by the observation of the 29-${\mathrm{cm}}^{-1\mathrm{}}$ absorption line of ${\mathrm{O}}^{16}$ impurities in silicon, so far only known from infrared spectra.

The flux-flow resistivity ${\rho }_f$ has been calculated for gapless superconductors with arbitrary amounts of magnetic and nonmagnetic scattering. The most striking result occurs in the limit of low concentrations of magnetic impurities, where the initial slope of ${\rho }_f$ with respect to the applied magnetic field may range from zero to infinity depending on the amount of nonmagnetic scattering.

Two-photon photogeneration has been observed in amorphous selenium. The field dependence of this uniform bulk photogeneration process saturates at low fields and fits a Poole-Frenkel model down to 300 V/cm. The previously reported strong field dependence of the generation efficiency at low fields for strongly absorbed light is attributed to surface recombination.