An exact finite-range calculation of the differential cross section has been performed for the two-step process ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}(p, d){}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}(d, t){}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}\left(3^{+}\right)$. It is found that finite-range theory differs from the conventional zero-range results by 20 to 40%, depending on the scattering angle.

Inverse Lamb dips caused by two-photon and multiphoton processes of infrared and radio-frequency radiations have been observed for methyl fluoride in a C${\mathrm{O}}_2$ laser cavity. The observations reveal interesting characteristics of the line shape and fine structures of Lamb dips which are explained by using Schimizu's theory. Analysis of the fine structure leads to identification of velocity-tuned multiphoton processes.

We report results of plasma confinement experiments with an auxiliary warm-plasma component flowing along magnetic field lines to suppress ion-cyclotron instabilities. The reduced plasma losses, with the lower fluctuation amplitude, permits neutral-beam build-up of a 13-keV deuterium plasma to densities as high as 4 × ${10}^{13}$ ${\mathrm{cm}}^{-3\mathrm{}}$ corresponding to peak beta values of 0.4. Variation of the beam energy demonstrates that longer confinement times are achieved at higher ion energies.

The transverse electromagnetic or filamentary instability is reconsidered in light of recent experiments which were unable to suppress the instability by increasing the beam transverse temperature. I find that only the applied magnetic field can stabilize the mode. While the beam temperature can cause stabilization in a collisionless, $\nu =0\mathrm{}$, plasma, for finite $\nu$ the beam is unstable to filamentation if ${{\omega }_{\mathrm{pb}}}^2{\beta }^2\gamma >{{\Omega }_{\mathrm{ce}}}^2$, regardless of its temperature.

We have injected short bursts of aluminum into the adiabatic-toroidal-compressor (ATC) tokamak, and measured the time evolution of the radial distribution of highly ionized states of aluminum. The results are compared with a computer code describing neoclassical impurity diffusion.

Critical attenuation measurements are reported for two anomalous acoustic modes near the 250°K transition of BaMn${\mathrm{F}}_4$. A mechanism for the transition involving rotations of the Mn${\mathrm{F}}_6$ octahedra about the orthorhombic $b$ axis is proposed, with a pair of phonons at the Brillouin zone $S$ points $\pi (0, \frac{1}{b}, \pm \frac{1}{c})$ being the soft modes. This mechanism, which suggests strong two-dimensional correlations, appears consistent with previous work on BaMn${\mathrm{F}}_4$ as well as with the ultrasonic data.

A general and physically simple model based on rigorous formulations of the dielectric function is presented and used to explain the phonon anomalies in niobium and niobium carbide. The model contains the explicit $q$ dependence of both the electron-phonon and electron-electron interactions for localized states near the Fermi energy and appears quite useful for explaining the $q$ dependence of phonon anomalies and lattice instabilities in various systems.

Neutron-elastic-scattering experiments performed on deuterated TTF-TCNQ single crystals reveal two structural transformations at 38 ± 0.5 K and at 54 ± 1.0 K. Below 38 K, a $4\overrightarrow{\mathrm{a}}\times 3.4\overrightarrow{\mathrm{b}}\times \overrightarrow{\mathrm{c}}$ modulation relative to the underlying undistorted lattice is established. At 38 K the modulation period in the $\overrightarrow{\mathrm{a}}$ direction becomes incommensurate and displays an abrupt decrease from its low-temperature value of $4\overrightarrow{\mathrm{a}}$ and gradually decreases with increasing temperature to $2\overrightarrow{\mathrm{a}}$ near 51 K.

The rule that the electron-hole-pair creation energy is 3 times the semiconductor band gap is extended to include a large group of insulators. It is used, together with the free-particle approximation, to describe cathodoluminescent phosphor efficiencies and the escape probabilities of secondary electrons.

Measurements of the temperature dependence of the carrier capture cross sections for ten deep levels in GaAs and GaP give strong evidence for nonradiative capture by lattice-relaxation multiphonon emission. A simple one-coordinate theory which takes into account the breakdown of the adiabatic approximation gives a good quantitative fit to the data.

For the first time there is experimental evidence for a distinct fine structure in the exciton spectrum of cubic semiconductors caused by envelope-hole coupling. As an example, we present measurements of the $2P$ exciton in cubic ZnSe by two-photon absorption. The highly resolved threefold energy splitting into $P_{\frac{1}{2}}$, $P_{\frac{3}{2}}$, and $P_{\frac{5}{2}}$ states is explained within a spherical model. We determine the spherical effective-mass parameter $\mu$ and give an upper limit for the cubic parameter $\delta$.

An expression is derived for the "primary" pyroelectric coefficient. In contrast to currently accepted theory, it is proportional to $T^3$ near absolute zero, and it depends on the anharmonic potential in the same way as on the second-order dipole moment.

The temperature dependence of the ratio of LO- to To-phonon-assisted recombination luminescence of the indirect exciton in silicon is reported. The ratio is found to differ from that observed in absorption and to vary from ∼ 0.3 at 2°K to ∼ 0.1 at 13°K. The variation of the ratio with temperature is shown to be due to the splitting of the ground state of the exciton by several tenths of a meV. The relevance of these results to the recombination from the electron-hole condensate in silicon is discussed.

We consider phase transitions in systems where the field conjugate to the order parameter is static and random. It is demonstrated that when the order parameter has a continuous symmetry, the ordered state is unstable against an arbitrarily weak random field in less than four dimensions. The borderline dimensionality above which mean-field-theory results hold is six.

We report an analysis of the Pioneer-10 data on Jupiter's magnetic field, in which the mass $\mu$ of the photon was treated as a free parameter. We set a limit of $\mu <~2\times {10}^{-11\mathrm{}} {\mathrm{cm}}^{-1\mathrm{}}\equiv 6\times {10}^{-16\mathrm{}} \mathrm{eV}\equiv 8\times {10}^{-49\mathrm{}} \mathrm{g}$. This is the smallest limit so far obtained from direct measurements. We compare our result with other published limits.

The differential cross section for ${\pi }^{\pm }$, $K^{\pm }$, and $p^{\pm }$ on hydrogen have been measured in the range $0.07<-t<\mathrm{}1.6\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The dependence on momentum, momentum, transfer, and particle type are discussed.

The alternative soft-pion approaches to threshold $\pi N\to \pi \pi N$ provided by the phenomenological-Lagrangian and current-commutator theories are shown to differ only in their pion-pole contributions. Since the data for the reaction ${\pi }^{-}p\to {\pi }^{-}{\pi }^{+}n$ seem well fitted by the former theory for $\xi =0\mathrm{}$, and by the latter for $\xi =-\frac{1}{2}$, where $\xi$ is the chiral-symmetry-breaking parameter introduced by Olsson and Turner, threshold total-cross-section data for this charge state will not be able to determine a unique $\xi$ value.

The cosmic-ray track that has been interpreted as a magnetic monopole may in principle be from a nucleus that underwent nuclear interactions. The a priori probability of this latter process is calculated to be ∼${10}^{-13\mathrm{}}$ if the particle moved at the reported velocity of $<0.6c$, but rises to ∼${10}^{-3\mathrm{}}$ if $0.7c$ is allowed. Among the number of cosmic rays already examined, the total predicted probabilities for observing such an interacting event would have been <7×${10}^{-13\mathrm{}}$ at $<0.6c$ and ∼2% at $0.7c$.

In a colored-quark and vector-gluon model of hadrons we show that a quark carrying nearly all the momentum of a nucleon ($x\approx 1$) must have the same helicity as the nucleon; consequently $\frac{\nu {W_2}^n}{\nu {W_2}^p}\to \frac{3}{7}$ as $x\to 1$, not $\frac{2}{3}$ as might naively have been expected. Furthermore as $x\to 1$, $\nu {W_2}^{\pi }\sim {\mathrm{}(1-x)\mathrm{}}^2$ and ${\left(\frac{{\sigma }_L}{{\sigma }_T}\right)}^{\pi }\sim {\mu }^2{Q}^{-2\mathrm{}}{\mathrm{}(1-x)\mathrm{}}^{-2\mathrm{}}+O\left(g^2\right)$; the resulting angular dependence for $e^{+}{e}^{-}\to h^{\pm }+X$ is consistent with present data and has a distinctive form which can be easily tested when better data are available.

Absolute cross sections for neutrons elastically scattered through small angles by Pb and U have been accurately measured at various energies in the range 7-14 MeV. The results disagree with many previously reported measurements and especially their interpretations regarding anomalous scattering. However, optical-model predictions based on the energy-independent, nonlocal potential of Perey and Buck are, apart from normalization, in agreement with the present measurements for Pb.