Experimental evidence for the production of a nuclear dipolar magnetic ordering in a high external field, where the nuclear spins are oriented at right angle to the field in the form of a helix which precesses around the field at the Larmor frequency, is presented.

It is shown that according to the standard hot-big-bang nucleosynthesis calculations, no single value of the ratio $\eta$ of baryon to photon number density can explain the right abundances of both ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{D}$. A slight neutrino degeneracy, however, provides a testable solution for $\eta$ which is in conformity with the current estimate of the baryonic component of the density parameter ${\left({\Omega }_N\right)}_0$ of the Universe.

The magnitude of the symmetry-breaking dimerization distortion has been determined by analysis of x-ray scattering data from trans-${\left(\mathrm{CH}\right)}_x$ $u_0\simeq 0.03$ Å.This distortion can account for the magnitude of the energy gap, implying that electron-electron interactions do not dominate the physics of long-chain polyenes.

This paper reports a high-resolution synchrotron x-ray scattering study of the freezing transition as a function of temperature and chemical potential of the two-dimensional continuous-symmetry system monolayer xenon on graphite. It is found that for a coverage of 1.1 monolayers the transition is continuous to within the substrate-determined resolution with fluid correlation lengths exceeding 100 atomic spacings. Comparison is made with current theories of solidification in two dimensions.

The first observation is reported of an absorption (dark) ESR signal specifically from unoccupied gap states within the space-charge region of $n$-type $a$-Si: H diode junctions. The detected resonance with $g=2.0053\mathrm{}\pm 0.0003$ is associated with the singly occupied dangling-bond defect. The applied-bias and temperature dependence identifies this signal with the well defined midgap defect band observed in deep-level transient spectroscopy. The results also imply a positive correlation energy, $U\gtrsim 0.2$ eV, between the singly and doubly occupied centers.

In considering the $\alpha -{\mathrm{CU}}_{100-x}{\mathrm{Ge}}_x$ alloys on the basis of a realistic muffin-tin Hamiltonian, the most notable feature of the electronic spectra is found to be the appearance of an impurity band below the host conduction band. In accord with relevant experiments, a Fermi surface is predicted to grow at approximately half the rigid-band rate for $x<\mathrm{}0.5\mathrm{}$ at.% Ge and essentially at the rigid-band rate for $x>\mathrm{}5\mathrm{}$ at.% Ge. This effect is related to a transition in the nature of states associated with the impurity band; these states are localized atomic $s$-like states for $x<~0.5$ and become delocalized in concentrated alloys.

The transmission coefficient for passage through a barrier with a parabolic maximum is computed rigorously when linear passive dissipation is present. The exact result for energies above and below the barrier height can be expressed in terms of the Coleman renormalized one-bounce time. The quasiclassical (WKB) approximation is recovered for energies significantly below the barrier height where "friction" enhances the tunneling probability.

With use of three-prong $\tau$ decays observed by the Mark II detector at the Stanford Linear Accelerator Center (PEP), the $\tau$ lifetime is measured to be (4.6±1.9)×${10}^{-13\mathrm{}}$ sec.

An ${{\eta }_c}^{\prime }$ candidate state is observed at a mass $M=3592\mathrm{}\pm 5$ MeV and with a natural linewidth $\Gamma <8\mathrm{}$ MeV (95% confidence level), by using the "crystal ball" NaI(Tl) detector at the Stanford Linear Accelerator Center (SPEAR). The evidence is found in the inclusive photon spectrum in decays of the ${\psi }^{\prime }\mathrm{}\left(3684\right)\mathrm{}$, where a signal is observed corresponding to a radiative transition to this state with branching ratio between 0.2% and 1.3% (95% confidence interval, including an uncertainty due to correlation with width).

Measurements of the energy and $t$ dependence of diffractive $\frac{J}{\psi }$ photoproduction are presented. A significant rise in the cross section over the energy range 60-300 GeV is observed. It is found that (30±4)% of the events are inelastic.

In a search for highly ionizing particles at PEP, Lexan and CR-39 plastic track detectors were exposed to an integrated luminosity of ∼${10}^{37}$ ${\mathrm{cm}}^{-2\mathrm{}}$ at an energy of 29 GeV in the center of mass. The search was sensitive to particles with magnetic charge $20e\lesssim g\lesssim 200e$ or electric charge $3\lesssim Z\lesssim 180$. An upper limit on the production cross section of $\sigma <0.9\mathrm{}\times {10}^{-36\mathrm{}}$ ${\mathrm{cm}}^2$ (95% C.L.) is obtained.

The random exchange of nucleons is seen to play a major role in the misalignment of angular momentum in heavy-ion collisions. It is further found that incorporation of Pauli blocking is very important for a quantitative explanation of the experimental data.

Methods have been developed to solve the time-dependent Schrödinger equation with Coulomb interactions, and applied to ${\mathrm{H}}^{+}$ and ${\mathrm{C}}^{+6\mathrm{}}$ collisions with H in the energy range 8-84 keV/amu. Total charge-transfer cross sections agree well with experiment, while ionization cross sections are higher than previous estimates at low energies. The phenomenon of "cusp asymmetry" is verified. Examination of charge-density plots reveals unexpected structures.

An isotope-selective technique has been used to measure line polarizations in the range 7.5 to 12.0 eV for the electron-impact-excited 185-nm transition of atomic mercury. Measurements were made on the $I=0\mathrm{}$ and $I=\frac{1}{2}$ nuclear-spin isotopes. A stepwise excitation technique was used involving electron excitation followed by single-mode laser excitation. The results obtained indicate a breakdown in the Percival-Seaton hypothesis near threshold.

Measurements of electron cyclotron emission in the whistler mode have been made on the Maryland mirror machine and the results are compared with hot-plasma theory. Good agreement is obtained, demonstrating, in particular, that the emission attains black-body levels for a wide range of conditions. It is concluded that this emission is a promising candidate to measure axial variations of the electron temperature in tandem mirror devices.

The $T=5\mathrm{}$ K isotherms of molecular ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ as well as the index of refraction to 370 kbar have been measured with a diamond-anvil cell. The hydrogens are somewhat softer than predicted from extrapolation of low-pressure measurements and the transition to the metallic atomic state is predicted to fall between 1.9 and 5.6 Mbar.

A link between (i) the Peccei-Quinn mechanism, (ii) the canonical fermion mass matrix, and (iii) minimal grand unification is established. The effects of a global versus a local horizontal U(1) symmetry are analyzed. It is pointed out that the weak $\mathrm{CP}$ nonconservation in such a model has to be accounted for by Higgs exchanges. A possible bridge to composite models is noted.

It is speculated that an almost stable state of hadronic and nuclear matter can be built from diquarks. It is suggested that this alternative form of matter has already revealed itself in existing experimental data in the form of a diquark "deuteron" with $J^P=0^{-}$ and with several other anomalous properties.

Twenty excitation functions for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$-, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$-, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$-, and ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$-induced fusion were deduced from measured neutron production cross sections. A global increase of the near-barrier fusion is observed as reactant masses increase, which by far cannot be accounted for by one-dimensional barrier penetration models. Static properties such as deformation introduce only small modifications to this tendency, whereas the mean curvature radius provides a good scaling to this phenomenon, thus indicating shape distortions or neck formation.

Nine vibration-rotation transitions of the fundamental band of ${\mathrm{HeH}}^{+}$ have been observed in absorption by using a tunable, infrared, difference-frequency laser source. The molecular constants for the $v=0\mathrm{}$ and $v=1\mathrm{}$ levels of the $X{}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ state have been determined and they agree very will with those derived from the ab initio calculation of Bishop and Cheung.