The splitting of the $\pi$ bands in graphite due to multilayer interaction has been observed directly for the first time for the valence-band states at $P$ and $Q$ on the vertical face of the Brillouin zone, using photoemission techniques. The splitting is found to be 0.8±0.1 eV for both $P$ and $Q$, giving a value of 0.42 eV for the parameter ${\gamma }_1$, in agreement with other experiments.

The electronic processes following optical excitation of $F$ centers in KCl are drastically changed if the $F$ electrons are spin polarized by magnetic fields at low temperatures (1.7°K). As the spin-aligned configuration of the $F^{\prime }$ center is forbidden, two effects appear: (1) The $F\to F^{\prime }$ conversion by conduction electrons becomes suppressed, and (2) the radiationless de-excitation of excited $F$ centers (caused by electron tunneling into neighboring $F^{\prime }$ center states) becomes suppressed, producing increases of the $F$ luminescence up to a factor 4.

Photoemission measurements of $f$ states and valence-band energies of EuS, GdS, and US for photon energies from 5 to 41 eV show characteristic energy-dependent emission strengths of "$p$," "$d$," and "$f$" states. These energy dependences permit the "$l$" character of various levels to be identified in many cases. For example, the emission strength of the $4f^7$ level in EuS increases about 100-fold relative to the 3-eV wide valence "$p$" band which lies just below the $4f^7$ level. GdS shows a deep $4f^7$ level at about 9 eV below the Fermi level $E_{\mathrm{F}}$, and US shows an "$f-d$" band at $E_{\mathrm{F}}$.

We have measured the temperature dependence of the dielectric constants for single-domain SrTi${\mathrm{O}}_3$ crystals. Dielectric anisotropies and deviations from the simple Curie-Weiss law have been observed and are discussed in connection with the structural phase transitions at 110 and 65°K.

The configurations $\pi h_{\frac{9}{2}}\nu g_{\frac{9}{2}}$ and $\pi h_{\frac{9}{2}}\nu i_{\frac{11}{2}}$ in ${}_{}{}^{210}{}_{}{}^{}\mathrm{Bi}$ have been studied using the $\gamma$-ray spectra following thermal-neutron caputre in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$. Comparison of the experimental energies of these configurations with those calculated by Kim and Rasmussen indicates a remarkable agreement.

Proton-$\gamma$ angular-correlation measurements at 19.6 MeV, together with asymmetry data for excitation of the first $2^{+}$ state of ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$, yield strong evidence for the full Thomas form of the spin-dependent collective-coupling potential. In addition, the agreement between these data and calculations is improved when the spin-dependent deformation ${\beta }_{\mathrm{s}.\mathrm{o}.\mathrm{}}$ is twice ${\beta }_2$, the deformation parameter for the central potential.

Total cross sections for ${\pi }^{-}p\to \Lambda K^0$ have been measured using optical spark chambers from threshold to $1.13-\frac{\mathrm{GeV}}{c}$ beam momentum in $19-\frac{\mathrm{MeV}}{c}$ intervals, but with a $1-\frac{\mathrm{MeV}}{c}$ resolution in the regions of the $\Lambda K$ and $\Sigma K$ thresholds. The behavior near $\Lambda K$ threshold indicates a significant $s$-wave contribution, but this experiment is unable to resolve any cusplike behavior in the region of the $\Sigma K$ thresholds. The cross section shows a broad peak in the vicinity of $1.05-\frac{\mathrm{GeV}}{\mathbf{c}}$ beam momentum.

The reaction $e+p\to e+p+{\rho }^0$ is measured by observing electron-proton coincidences for $\nu$ beyond the resonance region and for $-t=0.07\mathrm{} \mathrm{to} 0.5$ Ge${\mathrm{V}}^2$. We note that the yield of $p+{\rho }^0$ relative to other hadron final states is less than in photoproduction.

We have measured the ${K_L}^0$ mean life to be (5.154±0.044) × ${10}^{-8\mathrm{}}$ sec.

We have obtained a sample of 141 kinematically determined $\Lambda \to \mathrm{pe}\nu$ events. The internal-variable distribution for these events has been used to determine the magnitude of the ratio of the coupling constants, $\left|\frac{g_A}{g_V}\right|={0.75}_{-0.15\mathrm{}}^{+0.18\mathrm{}}$. The branching ratio was also obtained as (0.78±0.09)×${10}^{-3\mathrm{}}$.

We have measured the${\mathrm{He}}^4$-${\mathrm{He}}^4$ scattering cross section at 2.1 °K by an atomic-beam method. The value found for the averaged total effective cross section ${\overline{Q}}_{\mathrm{eff}}$ with both beam and scattering gas at 2.1 °K is 144 ${\mathrm{\AA }}^2$, with an estimated accuracy of 12%. We have also measured the total effective cross section as a function of beam velocity, $Q_{\mathrm{eff}}\mathrm{}\left(v\right)\mathrm{}$, with $v$ ranging from 70 m/sec to 210 m/sec. These measurements were made with the scattering gas at 2.1 °K.

The Glauber approximation has been applied to calculate the total and the differential cross sections of $1s-3d$ excitation of the hydrogen atom by electron and proton impact. The results obtained have been compared with other existing theoretical findings.

We report experiments which show that saturation of the inhomogeneously broadened 6328-Å neon-laser line is strongly affected by cross relaxation which tends to redistribute the excited atoms over the Maxwellian velocity distribution and thus leads to partially homogeneous line saturation. Our results for ${\mathrm{Ne}}^{20}$ discharges agree well with theoretical calculations based on a "strong-collision" model. Results for ${\mathrm{He}}^3$:${\mathrm{Ne}}^{20}$x mixtures show deviations from this model that we attribute to the "weak" cross relaxation caused by He-Ne collisions.

Measurements of dissipation versus velocity for the flowing helium film are reported. A new probe technique allows measurement of the dissipation as a temperature difference in a small region of the film. The data are interpreted in terms of the Langer-Fisher fluctuation model as modified for driven flow where we find $\Delta T\propto \exp \left[\beta \frac{{\rho }_s}{k\rho {\mathrm{Tv}}_s}\right]$.

The wave dispersion characteristic of whistler waves in a plasma is directly recorded as a function of the ratio of electron cyclotron frequency to wave frequency along their propagation path in a magnetic mirror. In the limit of small wavelengths the dispersion characteristic approaches that of plane waves in an unbounded plasma.

The specific heat and temperature derivative of the resistivity of $\beta$ brass have been simultaneously measured near its order-disorder transition and found to be proportional. An extension of the Fisher-Langer theory for magnetic transitions is used to explain the results.

Anomalous viscosity of electrons across the magnetic field in plasmas is calculated, assuming that the electrostatic ion acoustic wave is excited by the drift velocity of electrons parallel to the magnetic field lines. The mean free path of the wave perpendicular to the magnetic field is estimated. The momentum transfer rate between waves and electrons, ${\tau }^{-1\mathrm{}}$, also was calculated from the quasilinear theory. The anomalous (kinematic) viscosity was then estimated as $l^2{\tau }^{-1\mathrm{}}$. The theory appears to explain the experimentally observed results of the anomalous skin effect.

We examine a recent proposal by Goldstein for producing very low temperatures by freezing ${\mathrm{He}}^3$ in the presence of magnetic fields. We conclude that the highly isotropic nature of solid ${\mathrm{He}}^3$ will completely suppress the particular cooling mechanism envisaged, but a related magnetothermal effect should be observable. At readily accessible temperatures this effect will be small, but below about 1 mK a potentially useful amount of magnetic cooling is predicted. The field required for the maximum cooling is about 70 kOe.

The thermoreflectance of graphite has been measured in the energy range 4.4 to 5.5 eV at 80°K. Three peaks at 4.52, 4.76, and 4.82 eV have been identified as $M_1$-type singularities and assigned to transitions taking place at the points $Q$ and $L$ in the Brillouin zone.

A calculation has been performed which yields a good fit to the exponential absorption edge of Urbach's rule in ionic crystals. The major feature of this calculation is that its underlying physical mechanism offers a unified explanation of exponential absorption edges in all materials: ionic, covalent, and intermediate bonding crystals, as well as amorphous semiconductors.