Ultraviolet irradiation of thin (∼ 15-Å) laser-grown Si${\mathrm{O}}_2$ in vacuum renders the oxide unstable and it desorbs when heated to around 760 K. From electron spin resonance and Auger spectroscopy we conclude that irradiation produces a dense defect structure leaving thin films oxygen deficient, $\mathrm{Si}{\mathrm{O}}_x$ ($x<\mathrm{}2\mathrm{}$). Observed Auger-spectra modifications then correlate well with calculated band structures for defects in Si${\mathrm{O}}_2$.

Rate coefficients for reactions of the ions ${\mathrm{O}}^{+}$, C${\mathrm{O}}^{+}$, and C${\mathrm{H}}^{+}$ with atomic hydrogen have been measured for the first time at 300 K. This provides basic data for the ion chemistry of planetary atmospheres, cometary atmospheres, and interstellar molecular clouds. The ${\mathrm{O}}^{+}$+H measurement supports quantal calculations of this reaction. The C${\mathrm{O}}^{+}$+H reaction provides an example of partial spin nonconservation in a charge-transfer reaction occurring in a deep potential well. Reactions of the same ions with ${\mathrm{H}}_2$ that have been measured elsewhere are also reported.

Any matter unclustered on the supercluster scale must be "superhot" and became nonrelativistic only very recently. Such an unclustered collisionless background would dominate the radiation universe at nucleosynthesis and would later dampen the growth by gravitational instability of structure in the clustered component. If structure evolved by gravitational instability, the universe cannot be dominated by unclustered, collisionless, nonrelativistic dark matter, i.e., ${\Omega }_0\sim {\Omega }_{\mathrm{cl}}$ (observed for the clustered component). If indeed ${\Omega }_{\mathrm{cl}}=0.35\mathrm{}\pm 0.15$ then (barring a fine-tuned cosmological constant) the universe must be open, rather than flat.

Theoretical prejudices argue strongly for a flat Universe; however, observations do not support this view. We point out that this apparent conflict could be resolved if the mass density of the Universe today were dominated by (i) relativistic particles produced by the recent decay of a massive, relic particle species, or by (ii) a relic cosmological constant. Scenario (i) has several advantages in the context of galaxy formation, but must confront the problem of a young Universe.

The approach to equilibrium in a bistable system is governed by a small eigenvalue which appears to be difficult to compute. We show that supersymmetry makes possible an easy evaluation of this eigenvalue.

It is shown that anomalous diffusion (i.e., nonlinear growth of mean square displacements) can be caused by a specifically chaotic mechanism. It depends on deterministic diffusion and intermittency and gives rise to mean square displacements which grow asymptotically like $t^{\nu }$ with $0<\mathrm{}\nu <~1$ or like $\frac{t}{\ln t}$, depending on universality classes.

Riemann-Hilbert transforms, and their connections with the affine Lie algebra of Kac and Moody, and a two-parameter Bianchi-Bäcklund transformation are given for the constraint equations for the supersymmetric Yang-Mills fields. These are important integrable properties of the supersymmetric Yang-Mills fields; especially for $N>~3$ these constraint equations give equations of motion of the fields.

The branching fractions for the Cabibbo-suppressed $\tau$ decays are measured using the DELCO detector at PEP. The results, $R(\tau \to K{\nu }_{\tau })=(0.59\mathrm{}\pm 0.18)\%$ and $R(\tau \to K{\nu }_{\tau }+n{\pi }^0)=(1.71\mathrm{}\pm 0.29)\%$ including $n=0\mathrm{}$, are in agreement with the standard theory of sequential leptons and with $\tau -\mu -e$ universality.

Distributions of the Bjorken scaling variables $x$ and $y$, and the structure function $F_{+}\mathrm{}\left(x\right)\mathrm{}$, are presented both for neutral-current and for charged-current ${\nu }_{\mu }$ interactions. The data were obtained by use of the Fermilab 15-ft neon bubble chamber exposed to a narrow-band ${\nu }_{\mu }$ beam. Results are based on 151 neutral-current and 683 charged-current events. An important feature of the neutral-current analysis is the event-by-event reconstruction of the outgoing neutrino.

The surprising results of the recent 40-GeV/c Serpukhov measurement of the polarization in ${\pi }^{-}p\to {\pi }^{0}n$ are shown to support the conjecture that hadronic amplitudes may grow asymptotically as fast as they are permitted to by general principles.

This paper reports a study of $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\otimes \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R\otimes \mathrm{U}{\mathrm{}\left(1\right)\mathrm{}}_{B-L}$ gauge models with a completely general Higgs sector. The scalars which are consistent with the known low-energy phenomenology are determined. The results are used to obtain useful constraints on the $W_L-W_R$ mixing angle, $\xi$. In particular, the stringent upper limit $\xi <~0.002$ is derived.

The first measurements of the transverse spin-transfer coefficient $D_{\mathrm{NN}}\left(0\mathrm{}°\right)$ for intermediate-energy ($p$,$n$) reactions to well-resolved nuclear states are reported. Results are presented for ($p_{\mathrm{pol}}$,$n_{\mathrm{pol}}$) reactions on ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12,13,14}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ $E_p=160\mathrm{}$ MeV. The average value of $D_{\mathrm{NN}}\left(0\mathrm{}°\right)$ for pure Gamow-Teller transitions at this energy is shown to be close to the expected value of $\simeq -\frac{1}{3}$. The utility of spin-transfer measurements for investigation of aspects of the nuclear spin-dependent response not otherwise observable is pointed out.

The division of the excitation energy between the projectilelike and targetlike fragment was measured for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ + ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at $8.5A$ MeV incident energy. The excitation energy in the heavy fragment was determined from the mass asymmetry of fission fragments coincident with projectilelike fragments. For total energy losses between 30 and 70 MeV the excitation energy is found to divide more nearly equally than predicted by thermal-equilibrium models and is in good agreement with expectations based on nucleon-exchange models.

Nonequilibrium light particles were detected in coincidence with two fission fragments for ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$-induced reactions on ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at 420 MeV incident energy. Coincident binary-fission events were used to define the reaction plane and to suppress contributions from transfer-like peripheral reactions. A strong preference for the emission of nonequilibrium light particles in the fission plane was observed, suggesting the presence of an ordered transverse motion of the emitting source in the reaction plane.

An anomalously short mean free path of 10.93 ± 2.00 cm is found for secondary $Z=2\mathrm{}$ fragments of $4.5A$-GeV/c ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ projectiles at distances $D<~2.5$ cm from their production in nuclear emulsions. The largest contribution to this anomalous short—mean-free-path component comes from $N_h=0\mathrm{}$ interactions of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ in emulsion.

First experimental evidence for a low-lying $J^{\pi }=0^{+}$ excited state in ${}_{}{}^{192-198}{}_{}{}^{}\mathrm{Pb}$ is obtained by study of the $\beta$ decay of mass-separated Bi isotopes. It is shown that such excited states correspond to deformed two-particle, two-hole configurations.

Propagation of an intense relativistic electron beam (1 MeV, 27 kA, 30 ns) in vacuum after passage through a localized hydrogen plasma of ∼ 2-cm width has been observed. A large fraction of the injected current was found to propagate in a vacuum drift tube to a distance in excess of 50 cm downstream of the plasma. A description of the process is proposed which links the electron beam propagation with collective ion acceleration and which relates to cosmic-ray acceleration and laser experiments.

Measurements of the specific heat as a function of temperature at varying magnetic fields for the Kondo lattice systems Ce${\mathrm{Cu}}_2$${\mathrm{Si}}_2$ and Ce${\mathrm{Al}}_3$ reveal that, on an energy scale $\sim 0.5 \mathrm{K}\ll T_K$, there is structure which is due to the periodicity and is qualitatively changed by disorder in the alloys ${\mathrm{Ce}}_{0.9}$${\mathrm{Y}}_{0.1}$${\mathrm{Cu}}_2$${\mathrm{Si}}_2$, ${\mathrm{Ce}}_{0.8}$${\mathrm{Y}}_{0.2}$${\mathrm{Cu}}_2$${\mathrm{Si}}_2$, and ${\mathrm{Ce}}_{0.8}$${\mathrm{La}}_{0.2}$${\mathrm{Cu}}_2$${\mathrm{Si}}_2$. The results support the Fermi-liquid theory of Kondo lattices.

A saturation NMR method is introduced with which near a Zeeman-tunneling resonance the ratio of the Zeeman and tunneling specific heats as well as the Zeeman-tunneling coupling time can be determined. In addition, by measurement of the coupling time at different Larmor frequencies the tunneling splitting can be obtained with good accuracy (∼1%). This method is useful in the tunneling splitting range ${10}^{-2\mathrm{}}$ to 1 μeV, which is just below the resolution limit of inelastic neutron spectroscopy.

An experimental study of the magnitude of multiple scattering of the photoelectron in the x-ray-absorption near-edge structure is presented. Two types of multiple-scattering events are distinguished: type 1, in which the scattering atoms are approximately collinear with the center atom; and type 2, in which the various scattering atoms are far from collinear. Type 1, which is known to be important in the extended x-ray-absorption fine-structure range, has a similar importance in the x-ray-absorption near-edge structure range, while type 2 is important above the edge only when the bond distances are less than ∼ 1.6 Å.