Temperature dependence of the nuclear quadrupole frequency, ${\nu }_Q$, of noncubic metals has been studied theoretically. It is shown that the electronic contribution to the field gradient is largely responsible for the observed $T^{\frac{3}{2}}$ behavior. The conclusions are general and apply to all noncubic metals.

Landau quantum oscillations are observed for the first time in the layered, superconducting, incommensurate-charge-density-wave compound $2H$-Nb${\mathrm{Se}}_2$. The oscillations are observed clearly above $H_{c2\mathrm{}}$ but also below $H_{c2\mathrm{}}$, with somewhat increased scattering. This is interpreted as scattering of the orbiting normal electrons from the flux lattice. The observed sheet of Fermi surface can be explained if Mattheiss's augmented-plane-wave band structure is modified slightly.

The mixed-basis method has been used to compute the energy bands of an idealized $\beta$-cristobalite form of silicon dioxide. A direct-forbidden optical-absorption edge is predicted. Peaks in observed x-ray emission and optical-absorption spectra identified with critical points in the densities of states.

We have measured directly the relaxation time $\tau$ for the superconducting energy gap. We show that near the superconducting transition temperature ${\tau }_c$ the relaxation time diverges as predicted by several authors. By also measuring the equilibrium gap $\Delta$ we find $\tau \propto {\Delta }^{-1\mathrm{}}$ very near $T_c$ in agreement with the calculations of Schmid and Shön.

New, nonlinear, charged elementary excitations are predicted to occur for weakly pinned Fröhlich charge-density-wave condensates at low temperatures.

Photon-assisted tunneling is proposed for the investigation of optical plasma resonances; this is demonstrated by the direct observation of the Ag resonance in appropriate Ag-${\mathrm{Al}}_2$${\mathrm{O}}_3$-Al structures. A spectral scan of the ratio of the signals photoinduced by the $p$ and $s$ polarizations shows a large enhancement corresponding to the plasma resonance of Ag.

Sputtering yields for niobium bombarded by 12-MeV protons have been measured using a technique involving prior activation of the target material. Values obtained for backward and forward sputtering are $S_{\mathrm{B}}=(1.6\mathrm{}\pm 0.1)\times {10}^{-4\mathrm{}}$ and $S_{\mathrm{F}}=(4.7\mathrm{}\pm 0.3)\times {10}^{-4\mathrm{}}$, respectively. These values, expected to be similar to fast-neutron sputtering yields, are consistent with most recently published fast-neutron data.

A careful and systematic recomputation of the photon-photon scattering contribution to the muon magnetic-moment anomaly is made. The result is $\Delta a_{\mathrm{p}\mathrm{h}-\mathrm{p}\mathrm{h}}=(21.32\mathrm{}\pm 0.05){\left(\frac{\alpha }{\pi }\right)}^3$ leading to the theoretical value ${a_{\mu }}^{\mathrm{th}}=(1165\mathrm{}918\pm 10)\times {10}^{-9\mathrm{}}$.

We show that a careful conventional treatment of exchange currents in the calculation of the deuteron form factor [$0<~q^2<~8$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$] is not in contradiction with experiment. It rather shows an overall good agreement. We propose measurements of the deuteron form factor at momentum transfer much higher than $q^2\cong 100$ ${\mathrm{fm}}^{-2\mathrm{}}$ in order to obtain valuable information on the neutron form factor.

Using a spark-chamber magnet spectrometer and applying very stringent requirements to eliminate background contamination, we find three events of the rare process ${K_L}^0\to {\mu }^{+}{\mu }^{-}$ corresponding to a branching ratio relative to ${K_L}^0\to {\pi }^{+}{\pi }^{-}$ of ${4.2}_{-2.6\mathrm{}}^{+5.1\mathrm{}}$×${10}^{-6\mathrm{}}$. Using the branching ratio $\frac{({K_L}^0\to {\pi }^{+}{\pi }^{-})}{({K_L}^0\to \mathrm{all})}=0.21\%$, we calculate the branching ratio to be ${8.8}_{-5.5\mathrm{}}^{+10.7\mathrm{}}$×${10}^{-9\mathrm{}}$ (90% confidence level) for the ${K_L}^0\to {\mu }^{+}{\mu }^{-}$ decay.

In a search for optical rotation near the 8755-Å magnetic-dipole absorption line in atomic Bi, our first results set an upper limit $F<\mathrm{}{10}^{-6\mathrm{}}$ on a parity nonconserving amplitude associated with the line. This limit improves upon earlier parity tests in atoms by three orders of magnitude. Further improvement of at least another order of magnitude appears possible by this method which should then provide an exacting test of parity conservation in the neutral weak-current interaction in atoms.

In unified gauge theories with color (excitable by lepton probes), color effects become manifest in the asymptotic region through gluon terms. Several new results pertaining to these are derived and quantitatively discussed. These may be testable at energies higher than 50 GeV now available.

Two methods have been used to obtain values of the effective moment of inertia of very-high-spin ($20\hslash -50\mathrm{}\hslash$) states populated in heavy-ion compound-nucleus reactions. The ${}_{}{}^{162}{}_{}{}^{}\mathrm{Yb}$ nucleus studied has effective moments of inertia smaller than, but approaching, the rigid-body estimate.

Hypernuclear (${}_{\Lambda }{}^A{}_{}{}^{}Z_{}^{*}{}_{}{}^{}$) states exist which possess higher shell-model permutation symmetry than the Pauli principle allows for nuclear (${}_{}{}^A{}_{}{}^{}Z$) states and which are the lowest hypernuclear excitations in the appropriate valent configuration. The nature and location of these supersymmetric states and of strangeness-analog states are discussed within the framework of Sakata SU(3) symmetry restricted to $p$-shell configurations, for the hypernuclei ${}_{\Lambda }{}^9{}_{}{}^{}\mathrm{Be}_{}^{*}{}_{}{}^{}$ and ${}_{\Lambda }{}^{16}{}_{}{}^{}\mathrm{O}_{}^{*}{}_{}{}^{}$, for which observations have recently been reported.

The pressure-volume relationship for cerium monophosphide (CeP) has been determined to 200-kbar pressure. In this range the substance maintains the NaCl-type structure and exhibits abnormal compression. From the data we conclude that there is an electronic transition involving a change in the valence state of Ce from $3^{+}$ towards the $4^{+}$ state near 100-kbar pressure. Qualitative observations of the reflectivity of CeP under pressure support the valence transition. CeP under high pressure may be expected to exhibit superconductivity.

We describe measurements of the liquid-helium-flow behavior of Millipore (porous) disks. Our findings lead us to hypothesize a novel effect: Quantum vortices, "destroyed" when the superfluid passes through the porous material, deposit their angular momentum causing an observable, macroscopic torque on the disk. Many different aspects of our data are shown to be in excellent agreement with this model. We present measurements of the temperature and speed dependence of the vortex-induced torque.

We report a successful first-principles calculation of the correlation between crystal structure and $d$-electron-to-atom ratio in the transition-metal Laves alloys. The existence of a Hume-Rothery-type rule is related to geometrical similarities of the structures. The $d$-band binding is the main determinant of structure, and the common-band model is well obeyed, with a deviation whose physical interpretation we discuss. An experimental test is suggested.

Angle-resolved photoemission, using synchrotron radiation, from the chemisorption system W(001) + H shows a very large doublet of peaks at initial energies -1.3 and -0.6 eV for quarter-monolayer coverage which disappear at higher coverage. The emission lobes are strongly peaked in the $〈110〉$ azimuths and are attributed to essentially pure bulk W transitions. The electrons are emitted in the new directions through the influence of "extra" surface reciprocal lattice vectors associated with the hydrogen $c(2\mathrm{}\times 2)$ superstructure.

Electromagnetic radiation with a spectrum sharply concentrated near the bulk plasma frequency of silver has been observed in emission from Al-${\mathrm{Al}}_2$${\mathrm{O}}_3$-Ag planar tunnel junctions.

Experimental evidence is presented for a supercurrent oscillation arising from vortex motion in the flux-flow regime of superconducting films with periodically modulated thickness. An essential condition for detecting the rf electric field associated with the oscillation is matching of the vortex lattice to the periodic pinning structure represented by the thickness modulation.