We used the frequency analysis of the light scattered from a fluid to study the convective velocities in the Rayleigh-Bénard instability. The spatial dependence of the velocity is in agreement with theory. The behavior of the convective flow with the temperature seems to reach the predicted theoretical one only for $R>\mathrm{}1.5\mathrm{}{R}_c$.

End-on framing photographs taken at the Garching 500-kV theta pinch during fast magnetic plasma compression [$n_0=(1.5-4)\mathrm{}\times {10}^{13}$ ${\mathrm{cm}}^{-3\mathrm{}}$] show distinct radial filaments that are due to flute instabilities of high azimuthal-mode number. The observed wavelengths are of the order $\frac{c}{{\omega }_{p_i}}$ they decrease with increasing density, but no mass dependence is found. The flute instabilities are responsible for the existence of a plasma halo which surrounds the thermonuclear $\beta =1\mathrm{}$ plasma column and has a major influence on its behavior.

Evidence is presented that the mixed-state order parameter at surfaces parallel to the magnetic field is strongly modulated. The minima of this modulation act as the nucleation and denucleation sites for vortices.

Following pulsed laser excitation of Ge, we observe both the free-exciton (FE) and electron-hole-drop (EHD) luminescence decay. The kinetics are in excellent agreement with exact numerical solutions of the rate equations of Pokrovskii and Hensel, Philips, and Rice, yielding EHD and FE total lifetimes 35.6 ± 0.5 and 7.7 ± 0.5 μ sec, respectively, the EHD radiative enhancement factor $\rho =5.1\mathrm{}$, and values of the thermionic emission and backflow coefficients. The data suggest the production of EHD of diameter ∼ 0.4 mm.

The magnitudes, anisotropy, and temperature dependences of the three independent elastic constants of copper irradiated below 4 K with thermal neutrons provide evidence for the <100> split configuration of free interstitials and thermally excited resonance modes, and lead to a model for the configuration of the $I_C$ close-pair defect.

It is shown that a self-consistent Hartree-Fock treatment of the x-ray edge profile in metals modifies the singularity near threshold predicted by current theories. Some exact results are presented for the response spectrum of a charged Fermi liquid recoiling under a sudden applied potential. These do indicate a strongly asymmetrical spectrum of recoil energies for weak perturbations, similar to that predicted for noninteracting particles.

A detailed study of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\alpha ,{\gamma }_0){}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ from $E_x=12\mathrm{} \mathrm{to} 28$ MeV reveals a $T=0\mathrm{}$, $E2\mathrm{}$ strength which constitutes ≅ 17% of the sum rule in the ${\alpha }_0$ channel alone. Together with other results, ≅ 42% of this sum rule is accounted for in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. We estimate that the inclusion of other channels would raise this total strength to ∼ 70% and give an $E2\mathrm{}$ energy centroid and width both of ∼ 15 MeV.

The differential cross section of the reaction ${}_{}{}^2{}_{}{}^{}\mathrm{H}\mathrm{}(n,np)\mathrm{}$ was measured at ${\theta }_n=0\mathrm{}°$. Because of the applied special geometry the experimental data extend over a large fraction of the phase space, including several final-state interaction regions as well as regions far from the dominance of the quasi-two-body processes. This offers the possibility of extracting neutron-neutron scattering parameters and obtaining simultaneously additional information on the $N-N$ potentials and three-body forces in the frame of an exact three-body calculation.

The cross section for the phtotproduction of $\eta$ mesons by the Primakoff process has been measured at bremsstrahlung energies of 5.8, 9.0, and 11.45 GeV. A value of 0.324 ± 0.046 keV was obtained for the partial width of the $\eta$ meson decaying into photon pairs. This result is a factor of 3 lower than the previously accepted value.

It is shown how, in asymptotically free gauge theories, one can, given the deep-inelastic structure functions for values of $q^2$ in the asymptotic region, calculate explicitly the structure functions for all larger $q^2$. The ratio of structure functions for $q^2=50\mathrm{} \mathrm{and} 5$ ${\mathrm{GeV}}^2$ is estimated. Substantial deviations from scaling are found, as well as a dramatic $\omega$ dependence, for values of $1<~\omega <~4$.

The fermion-fermion scattering amplitude in non-Abelian gauge theories is calculated in the approximation of keeping only the leading logarithmic terms at high energy, up to eighth order in the coupling constant. The high-energy behavior of the calculated scattering amplitude is drastically different from the results obtained in other renormalizable field theories, e.g., the ${\varphi }^3$ theory and quantum electrodynamics.

We discuss properties of high-energy $p-p$ scattering in terms of models where the eikonal is a function of energy times a function of impact parameter (factorizable models). Using the eikonal determined from the data at one fixed energy, we deduce that the secondary diffraction maximum should rise with increasing energy if the total cross section rises. Further data, from National Accelerator Laboratory energies and up, would be of interest to decide for or against factorizable models.

Solitary wave solutions of field equations of the form ${\partial }_{\mu }{\partial }^{\mu }\varphi +m^2\varphi +\alpha {\varphi }^{2p+1}+\lambda {\varphi }^{4p+1}=0\mathrm{}$, with $p\ne 0, -\frac{1}{2}, -1\mathrm{}$, are developed. For vanishing interaction the solutions reduced to positive- or negative-frequency plane-wave solutions of the Klein-Gordon equation.

I consider the ratio of the total cross section for $e^{+}{e}^{-}\to \gamma \to N\pi$ with $2p$ visible prongs to that with two visible prongs. For any fixed $N$ and all $2p$, nontrivial and optimal lower isospin bounds are derived for these ratios. The preliminary data indicate that these bounds may be experimentally significant.

It is remarked that the recently observed near constancy of $\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})$ over a large range of center-of-mass energy may reflect the presence of a new class of short-range lepton-hadron interactions. This can be tested by a comparison of $e^{-}p$ versus $e^{+}p$ scatterings and a study of the spin, parity, and charge conjugation of the final product in annihilation as well as apparent deviations from scaling in $e^{\pm }p$ and ${\mu }^{\pm }p$ scatterings.

A theory of cooperative effects in ionic solids is presented, which points to the ionic carrier density as the main source of the anomalous behavior found in solid electrolytes. Depending on the parameter values, it predicts either an exponential increase of the conductivity with temperature, or a discontinuous change of the conductivity with an associated peak in the excess specific heat. The predicted behavior corresponds to that found in most solid electrolytes, particularly Rb${\mathrm{Ag}}_4$${\mathrm{I}}_5$.

We report the observation of Shubnikov-de Haas oscillations in the conductivity of surface holes in a $p$-type inversion layer of Si. The hole plasma is shown to be two dimensional. The effective mass varies from about $0.6m_0$ to $1m_0$ in the carrier concentration range (1 to 3.5) × ${10}^{12}$ ${\mathrm{cm}}^{-2\mathrm{}}$. It is proposed that the nonparabolic nature of Si valence band as well as many-body interaction affects the value of the effective mass. The hole gas is found to exist in one valley. Unexpected oscillations in the conductivity at low carrier concentration (less than 8 × ${10}^{11}$ ${\mathrm{cm}}^{-2\mathrm{}}$) are reported.

We report the optical absorption of Kr and Xe impurities in alkali-metal hosts. While the absorption threshold can be predicted accurately, the edge profile cannot be reconciled with current Hartree-Fock theories of optical excitations in metals.

The spin precession of the $1.1-\mu sec$ shape isomeric state in ${}_{}{}^{237}{}_{}{}^{}\mathrm{Pu}$ has been measured by the perturbed angular correlation method. From a measurement of the spin rotation frequency as a function of temperature of the target, the paramagnetic correction factor $\beta$ has been determined to be in agreement with the theoretical value of 2.86 at room temperature for a $4^{+}$ ionic state. The deduced value for $g$ is +0.14 ± 0.02.

The cross section for the process ${\pi }^{+}+d\to p+p$ is calculated using a $\pi -N$ $t$ matrix obtained from a Lagrangian formalism. The $t$ matrix is provided with a suitable cutoff to damp the large (off-shell) momentum components and the total cross section is found to be strongly dependent on the cutoff range parameter taken, i.e., to how fast the $t$ matrix falls off as it is taken off shell. It is argued that this is to be expected physically and that this sensitivity might provide a means of studying the $\pi -N$ off-shell $t$ matrix.