We have redetermined the crystal structure of ${\mathrm{K}}_2$[Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$]${\mathrm{Cl}}_{0.3}$·3${\mathrm{H}}_2$O. It crystallizes in space group $P4\mathrm{mm}$, contrary to earlier assignments. The ${\mathrm{K}}^{+}$ ions occupy ordered positions in layers with a periodicity of $c=5.77\mathrm{}$ Å which are perpendicular to the $c$ axis. The same kind of superstructure was found for ${\mathrm{K}}_2$[Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$]${\mathrm{Br}}_{0.3}$·3${\mathrm{H}}_2$O.

The significant contribution of phonon broadening to x-ray photoemission linewidths in polar materials has been experimentally verified. A simple theoretical expression is shown to account for the observed magnitude, temperature dependence, and variation with chemical environment of the photoemission widths.

The magnetic field structure of vortices in the mixed state of a lead-indium alloy and of niobium was probed by stopped ${\mu }^{+}$ particles. Fourier transforms of time-dependent spin-precession data contain a peak at the average internal field, which is also the applied field. For the alloy only there is a second peak at the saddle point of the internal field distribution. Motional averaging due to quantum diffusion of the muons at low temperatures can account for these results.

We have observed in ${}_{}{}^{126}{}_{}{}^{}\mathrm{Ba}$ a $K=0^{+}$ rotational band, extending to $I={18}^{+}$, exhibiting strong backbending above the ${10}^{+}$ state, and probably branching up to a second ${12}^{+}$ state. Another band with spins $7^{-}$, $9^{-}$, ${11}^{-}$, ${13}^{-}$, and ${15}^{-}$ was also seen. A similar negative-parity band was observed in ${}_{}{}^{128}{}_{}{}^{}\mathrm{Ba}$. Coriolis calculations reproduce the negative-parity bands in ${}_{}{}^{126,128}{}_{}{}^{}\mathrm{Ba}$ and other nuclei suggesting that they are decoupled two-quasiparticle (qp) states. The crossing of a similar decoupled positive-parity 2-qp band and the 0-qp band can explain the backbending and the two ${12}^{+}$ states.

A new theory of the rainbow is proposed and compared with the exact Mie solution. There is good agreement over a much broader range of angles and size parameters than for the Airy theory. The improvement is particularly remarkable for electric polarization. The treatment can be extended to atomic, molecular, and nuclear rainbow scattering.

We report the preliminary results of an experiment designed to search for the $C$-nonconserving decay of ground-state orthopositronium ($1{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$) into four photons. In terms of the branching ratio ${F_T}^{4\gamma }=\frac{{R_T}^{4\gamma }({}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}\to 4\gamma )}{R_{3\gamma }({}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}\to 3\gamma )}$, where ${R_T}^{4\gamma }({}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}\to 4\gamma )$ is the $C$-nonconserving four-photon decay rate and $R_{3\gamma }({}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}\to 3\gamma )$ is the $C$-conserving three-photon decay rate of free orthopositronium in our sample, we find ${F_T}^{4\gamma }<8\mathrm{}\times {10}^{-6\mathrm{}}$ (68% confidence).

We present measured distributions in the scaling variables $x$ and $y$ obtained from the reactions ${\nu }_{\mu }\left({\overline{\nu }}_{\mu }\right)+\mathrm{nucleon}\to {\mu }^{-}\left({\mu }^{+}\right)+\mathrm{hadrons}$ at high energy. The $x$ distributions are consistent with scale invariance. The $x$ and $y$ distributions are used to perform the first test of charge-symmetry invariance in high-energy neutrino interactions, assuming the validity of scale invariance. A possible effective deviation from charge-symmetry invariance is observed, which could be the result of new particle production.

Energy-dependent partial-wave amplitudes based on a coupled-channel ($K^{+}p, K\Delta$) $K$- matrix formalism are obtained for elastic $K^{+}p$ scattering up to $P_{\mathrm{lab}}=2\mathrm{}$ GeV/c. The data used include new high-precision differential cross sections. A total of 42 parameters describing the $l<~4$ partial waves are used to fit 3822 data points and the best solution found has a ${\chi }^2$ per degree of freedom of 1.33. This solution exhibits a $T$-matrix $Z^{*}$ resonance pole in the $P_3$ partial wave with mass coordinates 1787-$i100\mathrm{}$ MeV.

The photoionization yield or average charge produced per photon absorbed by Ne, Ar, Kr, and Xe has been measured from the threshold of double photoionization to 107 eV. The probability of double ionization is zero at threshold for the rare gases. For Ar, Kr, and Xe double ionization increases rapidly giving an abundance of 16 to 30% at 20 eV beyond the double-ionization threshold. In this region double ionization is constant or increasing slowly. At the threshold for triple ionization the average charge per photon increases rapidly.

Experiments are reported which measure directly the macroscopic transfer of energy from the surface of small crystallites to the interior via nuclear spins. The hydrogen nuclei in Y${\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{S}{\mathrm{O}}_4\right)}_3$·9${\mathrm{H}}_2$O constitute the nuclear spin system that transports the energy. We directly determine the value 5×${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^2$/sec (±20%) for the spin diffusion constant, which does not depend on the correctness of any theory of nuclear spin-lattice relaxation.

Heat pulse experiments at 1.8 K show the transmission coefficient of high-frequency phonons from silicon into superfluid helium to exhibit a maximum at a heater temperature of about 5 K.

A new kind of parametric instability is observed in a nonuniform plasma in which a resonant rf electric field and a density cavity grow simultaneously through mutual enhancements. The threshold is observed to be virtually zero and the growth rate is linearly dependent on pump intensity, ${E_0}^2$. Ponderomotive force and wave trapping are observed to be the mechanisms which drive the instability.

The recoilless-absorption spectra of the 21.6-keV $\gamma$ rays of ${\mathrm{Eu}}^{151}$ in ${\mathrm{Eu}}_x{\mathrm{La}}_{1-x}{\mathrm{Rh}}_2$ are composed of a few lines which exhibit strongly temperature-dependent isomer shifts. The results are interpreted in terms of fast fluctuations of electrons between a localized $4f$ level and the conduction band. The energy released by removing an electron from the $4f$ level to the conduction band (0.01-0.1 eV) depends significantly on the number of La nearest neighbors. The levels have a width of ∼ 0.01 eV.

It is shown that the ferromagnetic Ising model on a Cayley tree lattice exhibits a new type of phase transition at the field $B=0\mathrm{}$ below the Bethe-Peierls transition temperature $T_{\mathrm{BP}}$. The leading nonanalytic part of the free energy is of the form $B^{\kappa }$, where the "critical" exponent $\kappa \mathrm{}\left(T\right)\mathrm{}$ increases smoothly from one to infinity as the temperature goes from 0 to $T_{\mathrm{BP}}$. This implies a transition of "continuous" order $\kappa$.

A new decoupling procedure for the two-level induced-moment system in the paramagnetic regime is described. It offers improvements over the results of other methods and can in principle be extended to other systems.

The low-temperature isochronal annealing of lead after electron irradiation at 1.5 K shows the same discrete annealing steps observed in copper and silver. The major recovery stage (usually labeled $I_D$) occurs at 4.0 K.

The local theory for the photoyield resulting from $p$-polarized light incident upon a half-space photoemitter is reviewed and generalized to include nonlocal effects. Local and nonlocal yields for the electron gas are presented for frequencies above the plasma frequency. The nonlocal yields are substantially higher than the corresponding local yields and it is shown that this enhancement involves nondirect electronic transitions associated with both plasmons and single-particle excitations.

We report transmission electron-spin-resonance and EPR measurements on unbottlenecked $\mathrm{Al}$:Er dilute alloys. We have derived theoretical expressions for the effects of the exchange and crystal-field interactions on the properties of the resonances. A computer fit of these expressions to the data yields the crystal-field parameters, the sign, magnitude, and a measure of the $k$ dependence of the exchange interaction, and the spin-flip scattering cross section and free-ion $g$ value of the Er impurities.

We elucidate the relative roles played by the accumulation space-charge region and by the skin depth in determining the magnitude of the wave vectors of the coupled LO-phonon—plasmon modes which take part in Raman scattering in $n$-InAs at the $E_1$ gap.

Thermodynamic properties of the electron-hole liquid are calculated for five systems: Ge, Si, and Ge under large $〈111〉$ uniaxial stress, Si under large $〈100〉$ uniaxial stress, and GaAs. Important effects of multiple scattering and anisotropy are included in the correlation energy. For Ge, the ground-state energy, enhancement factor, compressibility, critical temperature, critical density, temperature dependence of Fermi energy, chemical potential, and equilibrium density are in good agreement with experiments.