A study of the nonradiative carrier recombination at individual interfacial dislocations between ${\mathrm{Ga}}_{1-x}{\mathrm{Al}}_x{\mathrm{As}}_{1-y}{\mathrm{P}}_y$ epitaxial films provides new information on the dislocation core structure. New analytical techniques allow to correlate the nonradiative and recombination properties of dislocations with their fine crystallographic configuration. The edge sessile dislocation is found to be electrically neutral. The absence of carrier recombination leads to a reconstructed core model with no dangling bonds.

The complex impedance of an aluminum film with normal-state sheet resistance of 4130 Ω/sq has been measured as a function of temperature and frequency. The experiment provides convincing evidence that there is a vortex-antivortex dissociation transition of the type predicted by the theory of Kosterlitz and Thouless for topological long-range order in two dimensions.

New magnetization data on the spin-Peierls system tetrathiafulvalene-Cu${\mathrm{S}}_4$${\mathrm{C}}_4$${\left(\mathrm{C}{\mathrm{F}}_3\right)}_4$ for $h<~155$ kOe and $T>~1.5$ K provide evidence for a new phase above $h\sim 115$ kOe. Considerable hysteresis in the field-induced transitions is observed for $T<~5.5$ K. These results are discussed in the light of current theoretical ideas.

It is shown that electromagnetic effects of a vector potential on a charged particle confined to a region $R$ (multiply or simply connected) are completely determined by field strengths in $R$, if the potential obeys certain conditions. Such potentials are adequate in experiments purporting to show Aharonov-Bohm effect. Therefore these experiments have not established effects of inaccessible fields.

The inclusive $\gamma$ and ${\pi }^0$ momentum distributions at the $\psi$ have been measured. Using these data and estimates of $\eta$ production, it is found that (4.1 ± 0.8)% of $\psi$ decays contain a direct photon with energy greater than 60% of the beam energy. The expected momentum distribution for direct photons calculated to lowest order in quantum chromodynamics is qualitatively different from that observed in the data.

In $\mathrm{pp}$ collisions at $\sqrt{s}=62.3\mathrm{}$ GeV where each proton fragments into at least one low-$p_T$, high-$x$ pion, no significant correlations for ${\pi }^{+}{\pi }^{+}$, ${\pi }^{+}{\pi }^{-}$, and ${\pi }^{-}{\pi }^{-}$ are found, thus excluding quark exchange with Brodsky-Gunion counting rules as the dominant interaction mechanism. This, together with the experimental $x$ dependence of single-particle spectra, suggests the introduction of a new counting rule, which is discussed.

Measurements of recognized ${\pi }^0$ production in $p$-Be collisions for $0.1<\mathrm{}{X}_{\perp }<0.5\mathrm{}$ and $-0.8<X_F<0.0\mathrm{}$ at 200, 300, and 400 GeV/c are presented. These invariant cross sections are fitted by $E\frac{d\sigma }{d{p}^3}=A{(1-X_R)}^M{P_{\perp }}^{-N}$ over this range of $X_{\perp }$ and $X_F$ with $M=4.88\mathrm{}\pm 0.14$ and $N=8.90\mathrm{}\pm 0.10$ independent of energy. No significant evidence for breaking of this scaling is observed over this large kinematic region at these energies.

A new method is proposed to quantize the dual-string theory. A diffusion equation is derived for the string functional where the area plays the role of the evolution parameter. Some exact string propagators are obtained.

Measurements of the two-body and three-body photodisintegration cross sections for tritium are reported. The measurements were done with monoenergetic photons, high-pressure gas samples, and neutron-multiplicity detection. Presently available theoretical calculations are not adequate to explain the results.

Static quadrupole interactions of three ${}_{}{}^{147}{}_{}{}^{}\mathrm{Gd}$ isomers in single crystals of hexagonal gadolinium have been observed. The quadrupole moments increase with increasing spin and imply a substantial (oblate) deformation ($\beta \sim 0.2$) for the 500-ns high-spin yrast trap.

Estimates of the Rb-${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ spin-exchange cross section have been obtained by observing the nuclear spin relaxation of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ in the presence of a Rb vapor. Nuclear spin relaxation of ${}_{}{}^{131}{}_{}{}^{}\mathrm{Xe}$ due to the presence of a foreign buffer gas and the relaxation rate on the glass walls of the cell have also been observed.

A two-photon technique is reported for the measurement of relative cross sections for the photolysis of simple molecules into particular product channels. In a demonstration of this method, two independently tunable dye lasers were used to dissociate molecules of ${\mathrm{Cs}}_2$ sequentially for wavelengths in the range 445 to 505 nm, and then to excite the resulting products to determine the relative cross sections for the photolysis of the ${\mathrm{Cs}}_2$ molecules into each of the energetically possible product states.

Disparate-mass neutral gases are here predicted to support two different forced-sound modes at moderately high frequencies, a fast and a slow wave. Specific predictions are given for mixtures of xenon and helium.

A description of strongly coupled plasmas, in which the direct correlation functions, $c_{\mathrm{ij}}\left(\mathcal{r}\right)$, are obtained by simple scaling from a universal function, is derived and found to be in full agreement with available computer simulation data, which it thus extends for arbitrary mixtures. It is thermodynamically consistent with the "ion-sphere" charge-averaging prediction for the enhancement factors for nuclear reaction rates, the results for which confirm the universality of the bridge functions for mixtures.

The spectral cascade processes in interchange-mode turbulence have been studied in the limit $k_{\parallel }=0\mathrm{}$. For positive-energy waves we find a cascade process towards smaller and larger $k_{\perp }$. We also obtain possibilities for up conversion. The conservation relations of the system are discussed.

The specific heat of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ adsorbed on Kr-plated graphite indicates the existence of an order-disorder transition from a (1×1) [½] triangular structure on a honeycomb lattice of adsorption sites. The specific heat singularity is logarithmic, as predicted from universality considerations, different from the power law observed in the $(\sqrt{3}\times \sqrt{3})R30\mathrm{}°$ order-disorder transition of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ on the bare graphite.

Sn impurity atoms have been selectively inserted on the two different substitutional lattice sites in the III-V semiconductors GaP, GaAs, GaSb, InP, InAs, and InSb. Radioactive ${}_{}{}^{119}{}_{}{}^{}\mathrm{In}_{}^{+}{}_{}{}^{}$ and ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sb}_{}^{+}{}_{}{}^{}$ ions which decay to the Mössbauer state of ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ have been implanted. From the isomer shifts determined in Mössbauer-emission experiments it is concluded that the implanted In and Sb ions selectively populate III and V sites, respectively.

Nuclear magnetic resonance splittings $\delta {\nu }_i\mathrm{}\left(T\right)\mathrm{}$ from deuterated molecules in liquid crystals are assimilated to vectors in a "space of molecular conformations," $\mathcal{E}\mathrm{}\left(T\right)\mathrm{}$, defined at each temperature $T$. The orientational parameters form a basis of $\mathcal{E}\mathrm{}\left(T\right)\mathrm{}$. An equivalence is established between temperature changes $T\to T^{\prime }$ and linear mappings $\mathcal{E}\mathrm{}\left(T\right)\mathrm{}\to {\mathcal{E}}^{\prime }\left(T^{\prime }\right)$, and used to explain a number of observations concerning the conformation of flexible molecules in liquid crystals. As an example, the invariance of certain "conformation coefficients" with temperature and phase transitions is theoretically demonstrated for the first time.

The first experimental measurements of the rate $\nu$ at which vortex rings are nucleated by negative ions in isotopically pure superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are presented. It is found that $\nu$ is considerably smaller than in the ordinary well helium employed in earlier work. By interpreting the data in terms of a generalized Landau argument values of the critical velocity $v_v$ for vortex nucleation and of a characteristic nucleation rate $R_0$ as functions of pressure $P$ in $16<~P<~25$ bar are deduced.

Atomic hydrogen has been stabilized at temperatures of 270±20 mK and in magnetic fields up to 7 T. It is believed to be gaseous. A sample displayed no measurable decrease in density after 532 sec. Covering of exposed surfaces with a film of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is essential.