Within the framework of weakly turbulent wave kinetics, a diffusion equation (in $\overrightarrow{\mathrm{k}}$ space) is obtained for the scattering of electron waves from a large-amplitude, narrow spectrum of ion waves. The evolution of the three-dimensional electron-wave spectrum is then studied for both isotropic and anisotropic ion wave backgrounds.

Experimentally verified, calculated Debye-Waller factors have been combined with a modified Lin-Kleinman pseudopotential and formalism to compute the temperature dependence of the PbTe direct band gap. The band-gap increase of 0.008 Ry between 100 and 300°K is in fair agreement with an experimental estimate of the explicit increase.

A set of coupled, nonlinear integro-differential equations is proposed to describe the space-time variation of the spin and phonon excitations in a paramagnetic crystal under conditions appropriate to a phonon avalanche. An effective phonon lifetime is derived and found to exceed the simple time-of-flight lifetime by orders of magnitude. For the case of an infinite slab, the theory is shown to be capable of remedying the inability of earlier models to describe the time evolution of the average magnetization.

The differential magnetoreflectance of the 5.5-eV exciton in RbI is observed for right-and left-hand circularly polarized light. An analysis of the Zeeman effect results in an effective $g$ factor of about 0.012. Explanations are offered for such an anomalously small $g$ factor.

A shell substructure has been resolved by Dean, Henry, and Frosch in luminescence spectra due to donors and acceptors in GaP. We can fit the substructure by considering the multipole fields of the donor and acceptor ions. A doublet structure in the type-I spectrum due to C + O can be explained by an octupole component alone, and fitting the data yields a measure of the ionic-charge delocalization.

When a current density $\overrightarrow{\mathrm{J}}$ and a magnetic induction $\overrightarrow{\mathrm{B}}$ are in the plane of a layer thin enough to quantize the motion perpendicular to the plane of the layer, the Hall voltage arises from deformation of the quantized states. If the layer is asymmetric, the Hall voltage will in general contain a term in $B^2$, as well as a term in $\overrightarrow{\mathrm{J}}\times \overrightarrow{\mathrm{B}}$. Numerical results are given for $n$-type inversion layers on (100) silicon surfaces.

The magnon density of states of ferromagnetic Gd${\mathrm{Cl}}_3$ in an external magnetic field has been observed by means of high-resolution optical spectroscopy. The relevant transitions arise from a single-ion transition mechanism, but the initial (magnon) and in some cases the final (exciton) states of the transitions are shown to have measurable dispersion, contrary to the usual description of rare-earth salts.

The average interaction of particles in a closed shell is consistent with the spectrum of the nucleus with two particles in the shell only if the correlations which are present in the two-particle case but not in the closed-shell case are considered. Realistic forces which induce large correlations give a sizable effect which is observable in the $d_{\frac{5}{2}}$, $d_{\frac{3}{2}}$, and $f_{\frac{7}{2}}$ shells. This may be interpreted as a repulsive effective three-body force.

A calculation of the forward-angle differential cross section for the reaction $p+A\to \mathrm{}(A-2\mathrm{})+p+d$ indicates that processes involving nucleons which are uncorrelated when the projectile initially interacts with the target are as significant as those processes involving correlated nucleons.

Ammonia has been found in the direction of the galactic center by detection of its $J=1\mathrm{}$, $K=1\mathrm{}$ inversion transition. The region of emission closely corresponds to the position, velocity, and size of strong OH absorption. Collisional and radiative excitation mechanisms are discussed. The column density of N${\mathrm{H}}_3$ and the kinetic temperature of the interstellar gas cloud are estimated to be 2×${10}^{16}$/${\mathrm{cm}}^2$ and 23°K, respectively.

A $J^{\mathrm{PC}}=0^{++}$ ${K_1}^0{K_1}^0$ enhancement at a mass of 1030±10 MeV with a width of ${45}_{-15\mathrm{}}^{+35\mathrm{}}$ MeV is observed in $\overline{K}N$ interactions. An $s$-wave resonance interpretation of this enhancement is favored over an $s$-wave scattering length effect. Within experimental uncertainties, we associate this enhancement with the $S^{*}$ observed in ${\pi }^{-}p$ interactions.

We have searched for the conversion of muonium to antimuonium, which would be allowed by a multiplicative muon number conservation law. The results are consistent with zero conversion rate, and set an upper limit to the magnitude of the weak-interaction coupling constant for the process of 5800 times the vector coupling constant of beta decay.

The reaction ${\pi }^{-}p\to f^{0}n\to 2{\pi }^{+}2{\pi }^{-}n$ has been observed at 5 GeV/c with $\sigma =11.5\mathrm{}\pm 4$ μb ($1.20<\mathrm{}{m}_{4\pi }<1.32\mathrm{}$, $\mathrm{}\left|t\right|<0.2\mathrm{}$ Ge${\mathrm{V}}^2$).

The decay of the ${Y_0}^{*}\mathrm{}\left(1520\right)\mathrm{}\to \Lambda +\gamma$ has been discovered in the reaction $K^{-}+p\to \Lambda +\mathrm{neutrals}$. The angular distribution and polarization of the $\Lambda$ are consistent with a pure electric dipole transition. The cross section yields a partial width for the decay of 0.15±0.03 MeV.

The differential and total cross sections for the reactions $\overline{p}p\to {\pi }^{+}{\pi }^{-}$ and $\overline{p}p\to K^{+}{K}^{-}$ have been measured at six laboratory momenta, ranging from 1.62 to 2.20 GeV/c. The ${\pi }^{+}{\pi }^{-}$ cross section falls from (137±16) to (32±8) μb over this interval while the $K^{+}{K}^{-}$ cross section falls from (51±10) to (21±6) μb. The center-of-mass angular distributions for the two channels differ remarkably.

A measurement has been made of the relative signs of the resonant $K^{-}p\to \Sigma \pi$ reaction amplitudes coming from partial waves corresponding to $\Sigma \mathrm{}\left(1385\right)\mathrm{}$, $\Lambda \mathrm{}\left(1405\right)\mathrm{}$, and $\Lambda \mathrm{}\left(1520\right)\mathrm{}$. From this it is shown that $\Lambda \mathrm{}\left(1405\right)\mathrm{}$ and $\Lambda \mathrm{}\left(1520\right)\mathrm{}$ are to be described as predominantly SU(3) singlets.

By representing a scattering amplitude as a sum of terms of the Veneziano type, we can cancel alternate trajectories and remain with trajectories spaced by two units of angular momentum. This result is obtained without imposing a supplementary condition and without introducing poles in the Regge residues at nonsense wrong-signature integers.

The first accurate measurements of nuclear moments in free atomic ions are now possible using an optical-pumping, exchange-collision method. In an experimental application of the method to ${\mathrm{Rb}}^{+}$, linewidths of a few hertz have been obtained.

Total differential scattering cross sections observed at 80° in the lab system versus incident energy for 12- to 100-keV ${\mathrm{P}}^{+}$, ${\mathrm{Cl}}^{+}$, ${\mathrm{Ar}}^{+}$, and ${\mathrm{K}}^{+}$ on Ar exhibit a similar characteristic structure. The structure is explained in terms of the kinematics of inelastic collisions occuring in the region of triple $Q$ structure in the Ar-Ar case. The existence of triple $Q$ structure in ${\mathrm{P}}^{+}$-, ${\mathrm{Cl}}^{+}$-, and ${\mathrm{K}}^{+}$-Ar cases is further supported by a calculation of $Q$ values involving theoretical Thomas-Fermi cross sections.

A new method is presented of resolving NMR structures in solids using dynamic nuclear polarization (the solid-state effect) methods. It is shown that NMR quadrupole and/or dipole structures which are completely unresolved in thermal-equilibrium NMR spectra can be resolved under dynamic nuclear polarization produced by saturating the center of an inhomogeneously broadened ESR line.