Paramagnetic susceptibility of the cubic crystal $\mathrm{O}_2^{}{}_{}{}^{+}$ ${\left(\mathrm{A}\mathrm{s}{}_{}{}^{\mathrm{V}}{}_{}{}^{}\mathrm{F}_6^{}{}_{}{}^{}\right)}^{-}$ between 4.2 and 300°K reveals a complete quenching of the orbital moment of the $2{p_{\mathrm{I}}}^{4}2{p_{\mathrm{II}}}^3$ configuration of the $\mathrm{O}_2^{}{}_{}{}^{+}$ molecular cation. No ordering of the $\mathrm{O}_2^{}{}_{}{}^{+}$ molecular cations has been detected in the range of measured temperature because of the large interatomic distance $\mathrm{O}_2^{}{}_{}{}^{+}$-$\mathrm{O}_2^{}{}_{}{}^{+}$ of 4.00 Å.

We measured optical absorption and magnetic susceptibility of amorphous ${\mathrm{As}}_2$${\mathrm{S}}_3$ as a function of temperature. An exponential variation of absorption constant with photon energy was found in the range $0.09<\mathrm{}\alpha <0.5\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. A Curie term in the susceptibility was shown to be characteristic of disorder in the vitreous material. A model relating the weak absorption tail to the susceptibility requires highly localized states having an exponential energy distribution in the gap.

Neutron crystal-field spectroscopy has been carried out in a series of praseodymium monochalcogenides and monopnictides; the results illustrate the power of inelastic neutron scattering techniques in such problems. It is found that all of the crystal-field levels in all compounds studied can be quantitatively accounted for by use of a simple point-charge model.

The energy-momentum dispersion relation within the forbidden gap of a single-crystal insulator (in this case, GaSe) has been accurately determined using a simple physical model to describe tunneling currents in appropriate thin-film structures. This dispersion relation, calculated from experimental current-voltage data, is shown to be intrinsic to GaSe and capable of quantitatively predicting tunneling currents. The work reported here represents the first quantitative calculation of tunneling currents in metal-in-sulator-metal structures with all parameters relevant to the experiment independently determined.

The Holstein-Boltzmann equation has been used to calculate the far-infrared absorptivity of normal Pb in and above the phonon-frequency region. The absorptivity exhibits a threshold at $\overline{\nu }\approx 35$ ${\mathrm{cm}}^{-1\mathrm{}}$ and weak structure at $\approx 70$ ${\mathrm{cm}}^{-1\mathrm{}}$ related to the transverse and longitudinal peak in the phonon density of states, respectively. It increases rapidly through the phonon region, eventually saturating at the Holstein value. These results agree with the recent experiments of Joyce and Richards.

In a study of the photoproduction reactions $\gamma p\to {\rho }^{-}{\Delta }^{++}$ and $\gamma n\to {\omega }^0{\Delta }^0$ at 4.3 GeV, we obtain a substantial cross section, 1.8±0.4 μb, for the first reaction and an upper limit of 0.5 μb for the second. If one-pion exchange dominates the above reactions, then by SU(3) one predicts ${\omega }^0{\Delta }^0:{\rho }^{-}{\Delta }^{++}=2:1\mathrm{}$. We believe that the discrepancy between theory and experiment is due to exchanges other than $\pi$ mesons contributing to charged $\rho$ photoproduction, thus making the derivation of $\Gamma \left(\rho \pi \gamma \right)$ from it rather unreliable.

The result of the Reines-Gurr experiment is analyzed in terms of nonderivative fourfermion interactions. Upper limits for interactions other than $V-A$ are shown to be lower than that for the $V-A$ interaction. In particular, leptonic neutral-current interactions of the vector or axial-vector type are already constrained to be below the strength of a Fermi interaction.

The first phase-band analysis of actual data is reported. Good solutions are obtained for ${\pi }^{+}-p$ scattering at considerably higher energies than conventional phase shifts have reached.

Angular distributions of charged secondaries in $\mathrm{pp}$ interactions for the energy range 100 to 800 GeV are compared with the predictions of the $\frac{d^{3}p}{E}$ distribution.

We predict the $x^0$ mass as well as the $\eta -x^0$ mixing angle using the broken chiral symmetry scheme. The basic input in the calculation is the Goldstone character of some of the pseudoscalar mesons in certain symmetry limits.

Making use of bootstrap equations for symmetry-breaking vectors in $(3^{*},3)\oplus (3,3^{*})$ and $(1,8)\oplus (8,1)$ representations of $\mathrm{SU}\mathrm{}\left(3\right)\mathrm{}\otimes \mathrm{SU}\mathrm{}\left(3\right)\mathrm{}$ with both octet and 27-plet electromagnetic and weak driving terms, and requiring partial conservation of vector current and the Cabibbo angle ${\theta }_c\ne 0$, we obtain a solution of the form of Gell-Mann, Oakes, and Renner for semistrong breaking interaction. Knowing the deviation from $\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}\otimes \mathrm{SU}\mathrm{}\left(2\right)\mathrm{}$ in their work, we get ${\theta }_c\approx 0.22$. The nonleptonic $\Delta S=1\mathrm{}$ interaction cannot be rotated away as it is in $(1,8)\oplus (8,1)$. Also the electromagnetic tadpole cannot be in $(3^{*},3)\oplus (3,3^{*})$ but can be in $(1,8)\oplus (8,1)$.

Inelastic energy-loss measurements for small-angle scattering in ${\mathrm{Ne}}^{+}\to \mathrm{Ne}$ and ${\mathrm{Ar}}^{+}\to \mathrm{Ar}$ collisions are reported. The resulting energy-loss spectra display a structure which may be explained in terms of curve crossing and preionization.

A new method for x-ray transition radiation detection by a streamer spark chamber is suggested. The use of the chamber secures a separate observation of both the radiation and the particle. It is shown that the mean number of the transition quanta linearly increases in the electron energy range 1.2 to 2.46 GeV. When plastic foam was used instead of a layered medium the efficiency of electron detection by transition radiation was 86%.

In a toroidal resistive plasma in the presence of a radial electric field one can obtain large perturbations of magnetic surfaces when the frequency of the azimuthal plasma rotation approaches the Alfvèn frequency.

Intense neutron production in a plasma-focus discharge begins when the visible plasma light fades abruptly. This correlation is interpreted in terms of enhanced plasma resistivity that causes Ohmic heating and permits a rapid constriction of the discharge current distribution; the latter phenomenon leads to deuteron acceleration resulting in intense neutron production.

Plasma heating by turbulent current flow has been studied by means of particle analysis. The spatial and temporal origin of hot ions is determined and compared with the temporal change of the resistivity and the amplitudes of the high- and low-frequency fluctuations in the plasma.

Optical and dielectric constants of Cs have been obtained above the plasma frequency by measuring reflectance as a function of angle at a Cs-substrate interface. We find a strong, broad peak centered at 5 eV in the conductivity $\sigma$. The peak is attributed primarily to plasmon-assisted transitions, though direct transitions may contribute to the overall absorption in this energy region.

A theoretical model is presented for both the permanent and transient ${E_1}^{\prime }$ centers in Si${\mathrm{O}}_2$ together with a mechanism for their optical excitation. The model presented involves the Heitler-London description of Si-O bonding. Experimental tests for verification of the model are discussed in some detail.

By the introduction of a deep center, a "polarizable" GaAs junction has been obtained which exhibits duplex or multiplex stable dc current-voltage characteristics. Each conduction state, "polarized" by a characteristic threshold voltage, appears to last indefinitely with low applied voltages at room temperature. This effect can be explained by assuming that the deep center, consisting of oxygen possibly in combination with other impurities, possesses an inherent bistability.

A deep defect level in a semiconductor is simulated by a large cluster of host atoms surrounding the defect. The electronic states of the entire system are then computed by linear combination of atomic orbital-molecular orbital techniques. The nitrogen donor in diamond is treated as an example. A large Jahn-Teller distortion is predicted which forces the donor state down close to the valence band, in good agreement with experiment. The calculated donor wave function agrees with EPR and electron-nuclear double resonence results.