The recently reported structured continuum of the $E\to B$ transition in ${\mathrm{I}}_2$ is analyzed to determine the $E$-state potential curve and the nature of the electronic transition moment. The minimum of the $E$ curve lies at 41 412 ${\mathrm{cm}}^{-1\mathrm{}}$ with $R_e=3.65\mathrm{}\pm 0.02$ Å, and the dipole transition moment decreases with increasing $R$ beyond ∼ 4 Å.

A specific coherence measurement technique is described, which yields the relative magnitudes of all predicted orientation and alignment parameters in tilted-foil-excited levels of ions and atoms. Quantum-beat frequencies and relative magnitudes are measured as a function of applied magnetic field strength and direction, and analyzed using Fano-Macek theory. The multipole moments of tilted-foil-excited 40-keV ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ $4d{}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ atoms are measured and related to proposed excitation mechanisms.

Differential scanning calorimetry measurements of the smectic-$A$—nematic latent heat of transition in binary mixtures of ${\mathrm{C}}_8$${\mathrm{H}}_{17}$O-${\mathrm{C}}_6$${\mathrm{H}}_4$-CHN-${\mathrm{C}}_6$${\mathrm{H}}_4$-${\mathrm{C}}_3$ ${\mathrm{H}}_7$ (8O.3) and ${\mathrm{C}}_2$${\mathrm{H}}_5$O-${\mathrm{C}}_6$${\mathrm{H}}_4$-CHN-${\mathrm{C}}_6$ ${\mathrm{H}}_4$-${\mathrm{C}}_3$${\mathrm{H}}_7$ (2O.3) strongly suggest the existence of a tricritical point at approximately 70 mole% 8O.3.

We report measurements of the rotational viscosity coefficient in the smectic-$C$ and nematic phases of heptyloxyazoxybenzene. The measurements are interpreted in terms of a model of the smectic-$C$ phase in which the molecules reorient about the normal to the smectic layers. Extrapolated to the nematic-smectic transition temperatures, the viscosity in the smectic-$C$ phase is lower by a factor of 0.4 than that in the nematic phase. A reverse pretransition effect is observed in the nematic phase.

A new extensive variable $A$ and its conjugate field II are introduced for the Kasteleyn dimer model on the honeycomb lattice via an isomorphic membrane-polymer chain model. The resultant phase diagram has a first-order phase line, thereby revealing a non-local order parameter in this model for the first time. The first-order line terminates in a critical point with critical exponents $\alpha ={\alpha }^{\prime }=0\mathrm{}$, $\beta =1=\gamma ={\gamma }^{\prime }$, and $\delta =2\mathrm{}$. The $\frac{3}{2}$-order exponents appear on the line $\Pi ={\Pi }_{\mathrm{critical}}$.

Measurements with a pulsed ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ atomic beam incident on the surface of liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at $T=0.03\mathrm{}$ K show that the probability of specular reflection depends only on the perpendicular momentum of the atom $\hslash kcos\theta$ and that it varies smoothly from 4×${10}^{-2\mathrm{}}$ to less than ${10}^{-4\mathrm{}}$ for $kcos\theta$ in the range from 0.05 to 0.6 ${\mathrm{\AA }}^{-1\mathrm{}}$. The probability of diffuse inelastic scattering is less than 2×${10}^{-3\mathrm{}}$. Contrary to theoretical expectations, there is no significant change in the reflection probability at the roton threshold at $k=0.5\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$.

A rotating relativistic beam of energy 500 keV and current 20-40 kA is injected into a preformed plasma of density $n_p$ between ${10}^{12}$ and ${10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$. It is observed that optimum coupling of beam energy to the plasma occurs at $n_p\gg n_b$, where $n_b$ is the beam density. The peak plasma temperature is about 1 keV. The heated plasma undergoes radial oscillations characteristic of the magnetosonic mode. The results are interpreted with a new theoretical model.

Stability against catastrophic radial collapse is demonstrated for initially well-behaved, localized solutions in a class of two- and three-dimensional wave equations characterized by saturating nonlinearities, which model various electrostatic and electromagnetic "caviton" structures in an asymptotically uniform plasma. This result contrasts sharply with mathematical predictions of equations with low-order nonlinearities. Discrete classes of possible quasistationary modes exhibit features comparable to atomic wave functions and differ qualitatively from one-dimensional structures.

A study of the effect of magnetic impurities and magnetic field on the purported charge-density-wave (CDW) transition in Nb${\mathrm{Se}}_2$ reveals an intriguing connection between the CDW and the superconducting states. Increasing magnetic impurity concentration results in a reduction of the transition temperature for CDW formation identical to the suppression of the superconducting $T_C$. A magnetic field, on the other hand, enhances the CDW transition.

Electron-spin polarization has been observed in low-energy electron diffraction from a clean tungsten (001) surface. Preliminary studies of the 01 beam at normal incidence and the 00 beam at incidence angles in the range 11° to 20° show significant spin polarization for electron energies from 45 to 190 eV. The polarization is sensitive to both the energy and the incidence angle of the unpolarized primary electron beam and ranges from -35% to +37%.

The low-energy-electron loss spectra of oxygen adsorbed at room temperature on clean Si and Ge (100) and (111) surfaces suggest that each oxygen atom is doubly bonded to a surface atom. Using a chemical-bonding argument, it is shown that this complex is also energetically more favorable than previously proposed oxidation models.

It is demonstrated that the force-distance profile for a dislocation and a single point defect can be determined from amplitude-dependent internal-friction measurements.

It is suggested that a single source of cosmic rays (supernovas) occurring in all galaxies can produce the observed spectrum and the observed anisotropy, and is predictable from supernova shock theory. Below ${10}^{13-14}$ eV the source and observed spectrum are the same, $N(>E)\mathrm{}\propto E^{-\alpha }$, $\alpha \simeq 1.75$. Above ${10}^{14}$ eV I predict a source with $\alpha \simeq 1.2$. Galactic leakage above ${10}^{15}$ eV is linear so that $\alpha \simeq 2.2$ as observed. Above ${10}^{19}$ eV cosmic rays fill the metagalaxy to a flux several times the anisotropic residual flux from a few events in our galaxy as observed.

We observe $\psi \mathrm{}\left(3684\right)\mathrm{}$ to decay into $\psi \mathrm{}\left(3095\right)\mathrm{}$ with a branching ratio of 0.57 ± 0.08. The branching ratio for the particular decay mode $\psi \mathrm{}\left(3095\right)+{\pi }^{+}+{\pi }^{-}$ is measured to be 0.32 ± 0.04. Remaining decays leading to $\psi \mathrm{}\left(3095\right)\mathrm{}$ are largely, but not entirely, accounted for by the mode $\psi \mathrm{}\left(3095\right)+{\pi }^0+{\pi }^0$ if the two pions in this decay are in a state of zero isospin.

We measure a limit on a parity-nonconserving asymmetry in the $p$-Be cross section at 6 GeV/c. The result is $\frac{({\sigma }_{+}-{\sigma }_{-})}{({\sigma }_{+}+{\sigma }_{-})}=(5\mathrm{}\pm 9)\times {10}^{-6\mathrm{}}$ where ${\sigma }_{+}\left({\sigma }_{-}\right)$ is approximately the $p$-Be total cross section for positive (negative) beam helicity. Systematic errors are determined to be <5×${10}^{-6\mathrm{}}$.

I consider the possibility that the newly discovered $e^{+}{e}^{-}$ resonances are members of a new class of heavy particles, distinct from the hadrons, whose interactions among themselves and with the hadrons are fundamentally different from the usual strong interactions. Experimental implications of such a picture, especially as contrasted with a charmed-quark model, are discussed.

In analogy with the Drell-Yan model for quark-antiquark annihilation into massive virtual photons, we study the possibility that the (presently) hypothetical pseudoscalar partner (${\eta }_c$) of the new vector resonance (${\varphi }_c$) observed at 3095 MeV is produced via gluon-gluon annihilation. This framework allows us to estimate cross sections for ${\eta }_c$ production in hadronic reactions and also suggests the interesting possibility of employing ${\eta }_c$ production as a probe of the distributions of gluons in hadrons. In addition estimates are made for the production of pairs of charmed hadrons.

Ten states of doubly excited He have been observed in a high-resolution electron-emission spectrum from 30-MeV ${\mathrm{O}}^{5+}$ +He collisions. Five lines can be identified as the $\mathrm{}\left(2pnp\right)\mathrm{}{}_{}{}^1{}_{}{}^{}D+\mathrm{series}$. The excitation mechanism is discussed and compared with results of an identical measurement using 4-MeV proton excitation.

A saturated-amplification method has been applied to the spectroscopic study of several infrared laser lines of xenon. The experiment is characterized by the use of two lasers. Linewidth at very low pressure, isotope shift, and hyperfine structure have been measured.

We have observed the Stark effect in the $5s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ and $4d{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2},\frac{5}{2}}^{}{}_{}{}^{}$ levels of sodium. Shifts as well as splittings were measured by use of two-photon spectroscopy in a short atomic beam. It was possible to separate uniquely the contributions from the neighboring $p$ and $f$ levels. The polarizabilities were found to be, in MHz/${\mathrm{}(\mathrm{k}\mathrm{V}/\mathrm{c}\mathrm{m})\mathrm{}}^2$, (a) $5s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$, ${\alpha }_0=5.2\mathrm{}\left(3\right)\mathrm{}$, (b) $4d{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}$, ${\alpha }_0=155.3\mathrm{}\left(1.7\right)\mathrm{}$ and ${\alpha }_2=-38.5\mathrm{}\left(7\right)\mathrm{}$, and (c) $4d{}_{}{}^2{}_{}{}^{}D_{\frac{5}{2}}^{}{}_{}{}^{}$, ${\alpha }_0=156.1\mathrm{}\left(1.3\right)\mathrm{}$ and ${\alpha }_2=-53.2\mathrm{}\left(5\right)\mathrm{}$. From this the oscillator strengths $f_{4d\to 5p}=0.274\mathrm{}\left(29\right)\mathrm{}$ and $f_{4d\to 4f}=0.018\mathrm{}85\left(24\right)\mathrm{}$ are obtained.