It is shown that the variation of electric potential with current density in superconductors depends on the band structure of the metal concerned and, contrary to the prediction of the free-electron model, can take either sign. At absolute zero the size of the effect can be calculated from the band structure alone, but its temperature variation is connected with the dependence of the order parameter on current density, and is harder to obtain.

The thermal conductivities $K_{\mathrm{es}}$ and $K_{\mathrm{en}}$ in the superconducting and normal states have been measured for four InBi films with Mn layers on each side. The slope of $\frac{K_{\mathrm{es}}}{K_{\mathrm{en}}}$ vs $t$ remains finite as $t\to 1$, as expected for gapless systems. The results indicate that there are states near the Fermi level, probably localized near the boundaries, which remain available at all temperatures.

Large quantum oscillations are observed in the thermoelectric emf in metallic tin at 1.3°K. These are correlated with magnetoresistance structure due to magnetic breakdown.

Amplification of 9-GHz longitudinal acoustic waves has been observed in $n-\mathrm{InSb}$ at 4.2°K on application of a pulsed electric field. The amplification results from a resonant transfer of energy between the conduction electrons and the acoustic wave since the mean free path is greater than the wavelength.

The resonant excitation in thin films of bulk plasma waves by incident electromagnetic waves is studied, and is shown to lead to structure in the reflectance, transmittance, and absorptance.

For the first time, angular-correlation functions of diatomic rotators in solids have been determined experimentally using vibration-rotation spectra. As samples we used ${\mathrm{OH}}^{-}$ and ${\mathrm{OD}}^{-}$ in KCl. Maxima and minima of the correlation function show an isotopic shift.

Two processes are observed in Nd${\mathrm{Cl}}_3$ whereby two excited ${\mathrm{Nd}}^{3+}$ ions undergo a transition leaving one ion in a higher excited state and the other in a lower state. In one case the initial states are the same, namely ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}$; in the other they are different, ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}$ and ${}_{}{}^4{}_{}{}^{}I_{\frac{15}{2}}^{}{}_{}{}^{}$. In both cases fluorescence decays of initial and final states are measured, allowing the determination of the rate equation for the processes.

We report the first clear evidence that rf magnetic fields generate acoustical side-bands in the Mössbauer spectra of metallic ${\mathrm{Fe}}^{57}$. We advance an explanation of this magnetoacoustic effect in terms of magnetostriction, and suggest that this effect provides a consistent explanation of the results of several earlier workers who observed rf resonance effects seemingly associated with hyperfine transitions.

Ellipsometric experiments have been performed on thick evaporated films of Na and K both by single reflection at free surfaces and by multiple reflection at metal-fused silica interfaces. The results are in qualitative agreement with the nearly-free-electron model, exhibiting no anomalous peaks and showing interband transitions with thresholds at the expected frequencies. The values deduced for the optical masses are $1.14m$ for Na and $1.17m$ for K.

High-resolution measurements of the energy distribution of neutrons critically scattered in Fe establish that the hydrodynamic region in which conventional theory is valid extends only to values of the scattering $q\approx K_1$, where $K_1$ is the inverse of the spin correlation range. Analysis of data restricted to this region indicates that the susceptibility varies as ${(1-\frac{T_c}{T})}^{1.30\pm 0.06}$. Contrary to expectations, the spin-diffusion constant $\Lambda$ shows considerably less dependence on temperature, varying as ${(1-\frac{T_c}{T})}^{0.14\pm 0.04}$.

We present a pseudopotential method for calculating very localized functions representing energy bands in molecules and solids.

We propose a new interpretation of the 110°K phase transition in SrTi${\mathrm{O}}_3$, in which the essential feature is a soft phonon at the corner of the cubic Brillouin zone. This interpretation is supported by new evidence from the temperature-dependent Raman spectrum as well as by results of earlier experiments and calculations. Several other experimental results are explained or predicted on the basis of our model for the phase transition.

Paramagnetic resonance of electronic states of atoms and radicals trapped in solid ${\mathrm{H}}_2$ and HD at 4.2°K after 4 × ${10}^6$ R of radiation damage have been investigated at 24 GHz. The apparent spin-lattice relaxation time of resonances of H atoms is damaged solid HD formed from gas containing 3 × ${10}^{-4\mathrm{}}$ ${\mathrm{O}}_2$ was found to be 0.14 msec at 4.2°K and approximately 0.27 msec at 1.2°K. Furthermore, these H atoms in solid HD remained stably trapped at 4.2°K for periods in excess of two months.

The empirical pseudopotential method is used to calculate the electronic band structure and the frequency-dependent dielectric function, ${\epsilon }_2\left(\omega \right)$, of NaCl. The results allow an identification of the interband transitions responsible for the prominent structure in the measured optical spectrum.

Using selective optical excitation under high dc fields, $F_A$ centers were aligned with respect to their optical-absorption tensors and microscopic inversion asymmetry. This ordering process removes the macroscopic inversion symmetry of the crystal, allowing the measurement of first-order electro-optical effects in the $F_A$ absorption. The analysis of the linear Stark effect provides information about size and sign of the dipolemoment difference between ground and excited $F_A$ states.

Measurements of the critical magnetic field curve of tungsten are presented and analyzed to determine the consequences of Abraham and Eckstein's proposed correction to the magnetic temperature scale for powdered cerium magnesium nitrate. The qualitative shape of the tungsten critical-field curve and the derived normal-state electronic specific-heat parameter $\gamma$ favor a considerably smaller temperature correction than that suggested by Abraham and Eckstein.

Giant Faraday and inverse Faraday effects accompanied by no energy loss are predicted for systems undergoing self-induced transparency. The size of these effects is calculated. These effects, and also the large velocity reduction which accompanies transparency, are shown to be intimately related to large energy storage in the resonant material system.

The cesiated (110) surface of $n$-type GaAs shows an unusually large temperature dependence of its work function. The reduction of the work function by 0.55 eV upon cooling from room temperature to 80°K is caused entirely by a change in band bending; the electron affinity remains constant.

The decay of ${\mathrm{Ca}}^{50}$ has been reinvestigated. The serious discrepancy between various theoretical calculations of ${\mathrm{Sc}}^{50}$ and earlier experimental results has been resolved by the observation of an allowed ${\mathrm{Ca}}^{50}$ $\beta$ decay to the 1848-keV level in ${\mathrm{Sc}}^{50}$. The $J^{\pi }=1^{+}$ assignment for this state and its $\gamma$-ray branching ratio are in good agreement with the recent theoretical treatment of ${\mathrm{Sc}}^{50}$ by Hughes and Soga.

The number of prompt neutrons and their average energies in correlation with fragment mass and kinetic energy have been measured directly for fission induced in ${\mathrm{U}}^{238}$ by 12-MeV protons. The sawtooth behavior evident for the average number of neutrons as a function of fragment mass (similar to the behavior in thermal neutron fission of ${\mathrm{U}}^{233}$, ${\mathrm{U}}^{235}$, and ${\mathrm{Pu}}^{239}$) disappears for events of low total kinetic energy.