Mössbauer-effect measurements have been performed on the alloy system ${\mathrm{Eu}}_x{\mathrm{La}}_{1-x}$ showing that for a sample with $x=1.2\%$ there is a transition to a magnetically ordered state at 660 ± 25 mK. The same sample shows a superconducting transition temperature of $T_s=2.15\mathrm{}\left(10\right)\mathrm{}$ K.

By comparing the predictions of the weak-coupling BCS theory with a general Ginzburg-Landau approach, we show that the weak-coupling model may give a qualitatively incorrect description of pairing with $L\ne 0$. Specific examples of the errors the weak-coupling model leads to are described for $d$- and $p$-wave pairing. In the latter case the general Ginzburg-Landau approach has structure enough to account for the current discrepancies between the weak-coupling predictions and the observed behavior of the low-temperature transition in liquid ${\mathrm{He}}_3$.

Low-temperature specific-heat and electrical-resistivity measurements show that the intermetallic compound ${\mathrm{Al}}_{10}$V has a local soft mode of characteristic temperature 22°K. The behavior is well described by an Einstein model. The number of such modes, taken together with x-ray evidence, indicates that the mode is associated with a loose Al atom occupying a large hole in the ${\mathrm{Al}}_{10}$V structure. This and other peculiarities of the structure provide evidence of important bonding effects.

A theory of infrared and Raman spectra, based on a two-parameter elastic energy and simple local-bond optical coupling mechanisms, is developed for amorphous silicon ($a-\mathrm{S}\mathrm{i}$) and amorphous germanium ($a-\mathrm{G}\mathrm{e}$). When the theory is applied to a random-network structural model the results are in satisfactory agreement with experiment, especially with regard to the qualitative differences between the infrared and Raman spectra. Results for simple microcrystalline models are also presented.

Longitudinal acoustic phonons have been measured by coherent inelastic neutron scattering in the direction of the platinum chains of a single crystal of the one-dimensional conductor ${\mathrm{K}}_2$Pt${\mathrm{}\left(\mathrm{CN}\right)\mathrm{}}_4$${\mathrm{Br}}_{0.3}$·3${\mathrm{H}}_2$O at room temperature. The phonon dispersion curve shows a pronounced anomaly at the phonon wave number $q_0=0.32\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$ and is interpreted as the logarithmic Kohn anomaly characteristic of a one-dimensional metal.

The perturbed angular correlation of ${}_{}{}^{111m}{}_{}{}^{}\mathrm{Cd}$ in antiferromagnetic KNi${\mathrm{F}}_3$, KCo${\mathrm{F}}_3$, and RbMn${\mathrm{F}}_3$ has been observed. The Cd hyperfine fields are interpreted to yield fractional spin densities of the Co-F and Mn-F bonds, $f_{\sigma }=2.6\mathrm{}$ and 3.8%, respectively. The latter value disagrees with neutron diffraction values.

From analysis of $V^0$ events observed in an exposure of the National Accelerator Laboratory 30-in. bubble chamber to $303-\frac{\mathrm{GeV}}{c}$ protons, we obtain these results: (1) $〈n_{\pi 0}〉$ rises approximately linearly with $n$-, implying strong coupling of neutral and charged pions, while $〈n_{K_S^{}{}_{}{}^0}^{}{}_{}{}^{}〉$ is less coupled to $n$; (2) $\gamma$, $K_S^{}{}_{}{}^0$, and ${\Lambda }^0$ production cross sections are approaching a scaling limit by 303 $\frac{\mathrm{GeV}}{c}$; (3) within the limited statistics, $\frac{d\sigma }{\mathrm{dy}}$ is flat in the central region for $K_S^{}{}_{}{}^0$ and low-multiplicity $\gamma$ events.

Excitation of the $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)$ state by 15-100-keV ${\mathrm{Li}}^{+}$ bombardment has been studied as a function of the angular scattering of ${\mathrm{Li}}^{+}$. The ratio of $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)$ to $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}P\right)$ excitations is about 0.6 and appears to be independent of both ${\mathrm{Li}}^{+}$ energy and scattering angle. Excitation of the $\mathrm{He}\left(2\mathrm{}{}_{}{}^1{}_{}{}^{}S\right)$ state indicates an inability of correlation diagrams based on the electron promotion model to predict all of the excitation products for ${\mathrm{Li}}^{+}$ + He collisions in this energy range.

The experimental impact-parameter dependence of the probability for copper $K$-shell ionization by oxygen projectiles with energies between 25 and 43 MeV is presented. The shape of the experimental curve at 43 MeV isfound to be quite similar to one calculated in the semiclassical Coulomb approximation.

Electron spin locking, rotary echoes, and rotary echo trains have been detected for molecules in their excited triplet states by monitoring the microwave-induced modulation of the phosphorescence. The preliminary results of these studies suggest that nuclear and electron spins in ground and excited states, acoustic phenomena in molecular solids, energy transfer, spin-exchange, nuclear polarization, and a wide variety of additional processes can be optically detected, measuring as few as ${10}^4$ spins.

A new argument is presented that yields the following criterion for plane shocks to be stable: $-1<j^2{\left(\frac{\mathrm{dv}}{\mathrm{dp}}\right)}_{\mathrm{H}}<1\mathrm{}$, where $j^2=\frac{(p-p_0)}{(v_0-v)}$ is the slope of the Rayleigh line, and ${\left(\frac{\mathrm{dv}}{\mathrm{dp}}\right)}_{\mathrm{H}}$ is the slope of the Hugoniot curve in the pressure-volume plane. The lower limit is well known and the consequences of its violation are well understood; however, no such degree of understanding has yet been achieved for the upper limit. It seems likely that it bears an important relation to detonation phenomena.

A plane, circularly polarized electromagnetic wave of finite transverse extent must have a longitudinal component of electric field intensity, as a consequence of $\Delta ·\overrightarrow{\mathrm{E}}=0\mathrm{}$. The magnitude of the resulting oscillatory, longitudinal force on plasma electrons may be large compared with other longitudinal forces. The associated periodic bunching of electrons along the laser axis results in large collective plasma effects.

Fully developed hydrodynamic turbulence is considered in terms of a steady-state solution to the exact Fokker-Planck equation for the probability functional of the velocity field. The nested intermittency argument of Yaglom is restated in this formulation. A divergent buildup of fluctuations during the energy cascade modifies the $k^{\frac{-5\mathrm{}}{3}}$ inertial subrange spectrum. A physical analogy of the critical exponent $\eta$ to the Yaglom intermittency parameter ($\frac{\mu }{9}$) is proposed.

An unstable launched wave on a low-density, cold-electron-beam-plasma system grows and traps the beam electrons. Test waves at neighboring unstable frequencies are observed to stop growing where the beam is trapped and to exhibit amplitude oscillations that are coherent with the amplitude oscillations of the main wave. The behavior of the test wave is calculated by regarding it as a slow modulation of the main wave's amplitude and phase.

We examine the three-wave decay instability due to a monochromatic pump with a phase which undergoes a random walk with diffusion coefficient $D$. Analytic results are obtained for small and large $\frac{D}{{\gamma }_0}$ (where ${\gamma }_0$ is the growth rate for $D=0\mathrm{}$), which demonstrate, respectively, a fractional reduction of $\gamma$ by $\frac{D}{{\gamma }_0}$ and a growth rate $\frac{{{\gamma }_0}^2}{D}$. Results are also presented for intermediate values of $\frac{D}{{\gamma }_0}$.

A similarity between the phase diagrams of systems which are believed to exhibit tricritical points and the phase diagram of the transition to the superconducting state of a thin film in a uniform magnetic field suggests the existence of a tricritical point in the latter system. The superconducting case is of interest because the field thermodynamically conjugate to the order parameter can be realized physically. The conjugate field plays an important role in models of the tricritical point but has been believed to be unphysical in systems studied thus far.

Cyclotronlike resonances have been observed in the far-infrared transmission spectra of centimeter-thick single crystals of bismuth.

For a symmetry-induced zero-gap semiconductor, such as gray tin, under uniaxial stress, the static dielectric constant at infinite wavelength and zero temperature is shown to contain a term of the form of $\delta _0^{}{}_{}{}^{\frac{-1\mathrm{}}{2}}$, where $2{\delta }_0$ is the stress splitting of the energy band at the band edge. The measured stress dependence of electron mobility of a degenerate $n$-type sample of gray tin at low temperature is explained in terms of this anomaloous screening.

It is shown that the recent thickness-dependence data on dielectric breakdown, obtained by the author and a co-worker, constitute evidence for Schottky-emission—dominated breakdown in thin films. Thus, the work presumably shows the interesting transition from the tunnel-emission—dominated breakdown to the Schottky-dominated one.

It has been observed experimentally that the density dependence of the energy gap of a tetrahedrally coordinated amorphous semiconductor is generally smaller than that of its crystalline form. Using the Ge 3 or ST12 structure as a simple model of amorphous Ge ($a-\mathrm{G}\mathrm{e}$), the electronic structure of this simple model of $a-\mathrm{G}\mathrm{e}$, calculated using the pseudopotential method, is obtained at several densities. The resulting density dependence is found to be small.