The nuclear $T_1$ has been measured between 1.2 and 300 K on ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{77}{}_{}{}^{}\mathrm{Se}$ in amorphous ${\mathrm{B}}_2$${\mathrm{O}}_3$, ${\left({\mathrm{Na}}_2\mathrm{O}\right)}_{0.3}$${\left(\mathrm{S}\mathrm{i}{\mathrm{O}}_2\right)}_{0.7}$, ${\mathrm{Na}}_2$${\mathrm{B}}_4$${\mathrm{O}}_7$, and Se. The measured rates, which for spins $I>\mathrm{}\frac{1}{2}$ are much greater than those observed in corresponding crystalline materials, are nearly field independent and vary as $T^{\alpha }$ with $\alpha \sim 1.3$. Such a quadrupolar relaxation might be explained by a model involving the distribution of two-level systems, as describes the anomalous thermal and ultrasonic-wave properties of similar materials.

A simple method, based on the direct transition model, has been developed for analyzing angular-energy-dependent photoemission data. Applying it to a pseudopotential band structure for GaAs all major structure in the experimental results from the (110) face can be accounted for and the wave vectors of the initial states are accurately determined. It is found that the umklapp scattering involving surface reciprocal-lattice vectors is important and that this mechanism may account for peaks previously attributed to surface states.

The transient-absorption spectra associated with the excited $F$ center in KCl, KBr, and KI are observed in the infrared. The absorption components observed can be ascribed to transitions from the relaxed excited state to the $3p$, $3d$, and $4p$ states of the $F$ center. The spectra show a series of multiphonon structures with a coupling constant less than unity, suggesting weak electron-phonon coupling of the transition in striking contrast to the $F$-band absorption.

New insights into the states involved in an organic charge-transfer reaction have been obtained by using in situ ultraviolet-photoemission-spectroscopy measurements to monitor valence-state binding energies during the reaction. For example, in forming ${\mathrm{Cs}}_2$-${\mathrm{}\left(\mathrm{TCNQ}\right)\mathrm{}}_3$, the transferred electrons are found to be strongly localized, with neither evidence for them occupying extended states nor evidence for fractional ionization of TCNQ. The $b_{1\mathrm{u}}-b_{2\mathrm{g}}$ energy gap of TCN${\mathrm{Q}}^0$ is greatly reduced (about 2 eV) upon anion formation.

Energy-distribution spectra have been measured for secondary electrons backscattered into a narrow angle about the normal direction to three tungsten-single-crystal faces, viz. (100), (110), and (111). Improved spectral resolution provides evidence for emission from excited states located above the vacuum level, the intensity of emission being related to one-dimensional density-of-states features along the corresponding low-index symmetry lines. Good agreement with a calculated energy-band structure is observed.

In angle-resolved secondary-electron—emission spectra from a silicon (111)7×7 surface there are two series of peaks which are not in the spectra of the unreconstructed (111)1×1 surface. These peaks are interpreted by a two-step model; electrons are excited into surface-state resonances lying above the vacuum level, from which states they emerge into the vacuum. The dispersion curves of these states are presented and discussed.

The relativistic one-boson-exchange potential of Holinde, Erkelenz, and Alzetta is used to calculate the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ binding energy ($E_3$), wave function, and charge form factor. The calculation uses the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{}(S-D)\mathrm{}_1^{}{}_{}{}^{}$ two-nucleon states and all the three-nucleon states that can then occur. The binding energy was found to be 6.75 MeV; the wave function composition was $P\left(S\right)=92.8\mathrm{}$, $P\left(S^{\prime }\right)=1.6\mathrm{}$, and $P\left(D\right)=5.7\mathrm{}$; and the form factor had a diffraction minimum at $Q^2=16.8\mathrm{}$ ${\mathrm{fm}}^{-2\mathrm{}}$ and a secondary maximum of strength 5.8×${10}^{-4\mathrm{}}$ at $Q^2=22.8\mathrm{}$ ${\mathrm{fm}}^{-2\mathrm{}}$.

Recent analyses of (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$) four-nucleon transfer data in the $s-d$ shell have suggested (a) that the transfer occurs with the $\alpha$ cluster in its 28.5-MeV excited state, and separately (b) that weakly absorbing optical potentials must be used. Our analysis of four-nucleon transfers measured in the reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$(${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$)${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ contradicts such peculiar features in the (${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$) reaction, and yields spectroscopic information in agreement with theoretical predictions.

The ($K^{-}, {\pi }^{-}$) reaction on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ at $p_{K^{-}}=390\mathrm{}$ MeV/c with forward emitted ${\pi }^{-}$ (Feshbach-Kerman kinematics) was studied. Formation of ${}_{\Lambda }{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{\Lambda }{}^{27}{}_{}{}^{}\mathrm{Al}$ was observed. Experimental energy spectra are compared with some theoretical predictions.

Results on charge and multiplicity fluctuations in 205-GeV/c $\mathrm{pp}$ interactions are presented. The data are shown to be consistent with a simple picture of independent emission of low-multiplicity clusters, rather than of single pions, for the major part of the inelastic $\mathrm{pp}$ cross section.

Backward meson production in the reaction ${\pi }^{-}p\to p{\pi }^{-}{\pi }^{+}{\pi }^{-}$ has been studied with use of a streamer chamber triggered by the detection of a fast forward proton. For ${cos\theta }^{*}<-0.98\mathrm{}$ we find no evidence of $A_1$ or $A_2$ production, and we determine total backward cross-section upper limits (95% confidence) of 0.93 and 0.72 μb, respectively. At $m_{3\pi }=1.9\mathrm{}$ GeV/${\mathit{c}}^2$ we observe a broad enhancement of about 3-standard-deviation significance. Evidence for backward quasi-two-body production is seen in the ${\rho }^{0}p{\pi }^{-}$ and $f^{0}p{\pi }^{-}$ channels.

Using a classical Soret cell and the beam-deflection technique, we have, for the first time, accurately determined the nature of the divergence of the thermal-diffusion ratio $k_T$ near the consolute critical point of the aniline-cyclohexane mixture. Furthermore, having measured with the same technique the diffusion coefficient $D$, we have also determined the behavior of the thermal-diffusion coefficient $D_T=k_{T}D$. The thermal-diffusion ratio diverges as a function of $T-T_c$ with a critical exponent close to that of the long-range correlation length $\xi$, while $D_T$ is practically constant at 4.5×${10}^{-6\mathrm{}}$ ${\mathrm{cm}}^2$/sec.

Pulsed-NMR measurements of the longitudinal spin-relaxation time $T_1$ in superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ are reported which indicate that new and very unconventional relaxation mechanisms exist below $T_c$. In $A$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$, $T_1$ decreases very rapidly below $T_c$ and the magnetization recovery from saturation is linear in time. In $B$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$, the magnetization recovery is exponential in time, but the relaxation rate $\frac{1}{T_1}$ is linear in applied field gradient. Possible explanations of these phenomena are discussed.

The phase transition of the classical $\mathrm{XY}$ model on a triangular lattice is studied with a renormalization-group technique based on the cumulant-expansion method of Niemeijer and van Leeuwen. By utilization of some approximations, a nontrivial fixed point is located, and this yields the following critical values: $\frac{J}{k{T}_c}=0.25\mathrm{}$, $\nu =1.35\mathrm{}$, and $\eta =0.21\mathrm{}$.

I have performed computer simulations of high-density, spherical shells containing DT gas, irradiated by pulsed electron beams. For these targets, (1) the optimal shells are thick enough that few electrons reach their inner surface, (2) the low-level bremsstrahlung which penetrates the shell significantly affects the target performance, (3) breakeven requires about ${10}^{15}$ W deposited for 5 nsec. This represents a considerable improvement over the behavior of bare DT spheres; further improvements may reduce the power to ${10}^{14}$ W.

A quiescent equilibrium state of a non-neutral beam ring may have been realized when a relativistic electron beam (450 keV, 16 kA, 25 nsec) was injected parallel to a toroidal magnetic field in vacuum. The longest lifetime obtained was 20 μsec which corresponded to 3000 revolutions of the electrons around the torus. The lifetime was limited by the appearance of an ion-resonance instability.

The inorganic crystalline polymer polysulfur nitride has been found to become superconducting with a transition temperature of (0.26±0.03)°K.

A nonlinear extension of the bond-charge model is used for the analysis of the infrared and Raman spectra because of phonons in diamond, silicon, and germanium. The infrared absorption of these crystals is explained by the anharmonic coupling between the bond charges and their neighboring ions. The first- and second-order Raman spectra are described successfully by means of bond polarizabilities. The relation of the model parameters to the photoelastic constants and band structures is discussed.

By use of an yttrium aluminum garnet laser operating at 2.1 μm, polarized transmission Raman spectra of Ge(As) have been measured for impurity concentrations spanning the Mott transition. The valley-orbit Raman line broadens markedly at the transition; its line shape has been fitted using the London-Heitler method. The spectrum in the metallic regime constitutes the first observation of single-particle scattering from intervalley fluctuations.

The dispersion relations for magnetic excitons propagating on the hexagonal sites of double-hcp Pr provide clear evidence for a pronounced anisotropy in the exchange. The energy of the excitations decreases rapidly as the temperature is lowered, but becomes almost constant below about 7 K, in agreement with a random-phase-approximation calculation. No evidence of magnetic ordering has been observed above 0.4 K, although the exchange is close to the critical value necessary for an antiferromagnetic state.