We study a one-dimensional random Kronig-Penney model in the presence of a constant electric field. We rigorously prove for the first time the existence of a transition between a regime of extended states for large field and a regime of power-localized states for small field. There the large-distance behavior of the states is ${\mathrm{}\left|x\right|\mathrm{}}^{-\alpha \mathrm{}\left(F\right)\mathrm{}}$ with $\alpha \mathrm{}\left(F\right)\mathrm{}\sim \frac{C}{F}$ for small field $F$, confirming a numerical computation of Soukoulis et al.

A covariant, symplectic, classical dynamical system is presented whose quantization, by replacement of the Poisson brackets with commutators, gives precisely the Dirac electron theory. For the classical system the velocity and momentum are independent dynamical variables, as in Dirac electron; it undergoes a real Zitterbewegung so that the spin is the orbital angular momentum of the Zitterbewegung. Thus the longstanding problem of representing the configuration space of quantum spin by a classical model is solved. Three different forms of the dynamical equations are given.

The most precise determination of the magnetic moments of the electron and positron come from a University of Washington $g-2\mathrm{}$ experiment. The accuracy of this experiment has now been improved to the stage where a detailed theory of the line shape is required in order to determine the moments with comparable precision. We present here the results of this theory.

We study the phenomenon of spontaneous compactification for the case of anomaly-free gauge theories in six dimensions with manifold $M_4\times S_2$ and in eight dimensions with manifold $M_4\times S_4$. For the latter case, we show how to obtain, for example, Georgi's three-family SU(11) theory in Minkowski space, $M_4$.

We have used an electronic tracking system to measure the lifetime of $D^0$ mesons produced in $e^{+}{e}^{-}$ annihilation at 29 GeV. Based on a sample of 27 events, the lifetime is found to be (${4.2}_{-1.0\mathrm{}}^{+1.3\mathrm{}}$±1.0) × ${10}^{-13\mathrm{}}$ s.

The missing-mass spectra for the transfer reactions $p({}_{}{}^3{}_{}{}^{}\mathrm{He},d)X$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}\mathrm{}(p,d)X$ ($B=2\mathrm{}$, $T=1\mathrm{}$) have been measured at, respectively, $T_{{}_{}{}^3{}_{}{}^{}\mathrm{He}}=2.7\mathrm{}$ GeV and $T_p=0.925\mathrm{}$ GeV. The data show a narrow structure lying on top of an important continuum, with a mass $M=2.240\mathrm{}\pm 0.005$ GeV and a width ${\Gamma }_{\frac{1}{2}}=0.016\mathrm{}\pm 0.003$ GeV.

Coincidence measurements of two nucleons from the reactions ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\gamma ,pn)X$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\gamma ,pp)X$ have been made in the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ resonance region with a tagged-photon beam. From the momentum and angular correlations between the two nucleons, two quasifree reactions, $\gamma +{}_{}{}^{\prime \prime }{}_{}{}^{}p{n}^{\prime \prime }\to p+n$ and $\gamma +{}_{}{}^{\prime \prime }{}_{}{}^{}p{p}^{\prime \prime }\to p+p$, are clearly identified. The separation energy and the momentum distribution of the quasifree deuteron in ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ are determined together with the ratio between cross sections of the two quasifree reactions.

Optical pumping in fast ion-beam collinear laser spectroscopy is used to study the time evolution of oriented metastable state populations in an external magnetic field. A theoretical description of this time-differential ground-state Hanle effect is presented. The possibility to measure ionic ground- and metastable-state $g$ factors is illustrated by a measurement of the $g$-factor ratio of the $5d{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}$ and $5d{}_{}{}^2{}_{}{}^{}D_{\frac{5}{2}}^{}{}_{}{}^{}$ states in ${\mathrm{Ba}}^{+}$.

With a three-level configuration in ytterbium vapor, we have performed the first quantitative investigation of single excited-level scattering using a stimulated photon echo (three-pulse echo). We have studied the collisional relaxation of the echo signal by rare-gas perturbers and have derived a theoretical expression for the relaxation rate. Total elastic cross sections for collisions between $\mathrm{Yb}(6s6p{}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$) and Ne or Xe have been obtained.

The nuclear physics aspects of the $d-d$ reactions initiated by low-energy polarized deuterons are discussed. It is shown that the use of polarized deuterons does not suppress the fusion of deuterons with deuterons and hence does not suppress neutron production. Therefore a recently proposed "neutron-free" $d$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ fusion reactor is unlikely to work.

We show that sustained plasma discharges in the ZT-40M reversed-field pinch experiment can be explained in terms of electron wander in a stochastic magnetic field. We indicate results of a Fokker-Planck calculation for nonlocal electrical conductivity in slab geometry and show that this approach can account for the key anomalies of reversed-field pinch behavior, without needing to invoke a "plasma dynamo."

Pulsed-infrared-laser time-of-flight mass spectrometry has been applied to investigate photodesorption of N${\mathrm{H}}_3$ adsorbed on a Cu(100) surface at 90 K. Desorption from monolayer and multilayer surface coverages due to resonant ${\nu }_s$ stretching vibrational excitation has been observed. Both single-photon and multiphoton excitation processes are examined and the molecule-surface interaction dynamics associated with the desorption phenomenon is discussed.

Simple methods are described to evaluate quantitatively the influence of charge-density-wave fluctuations on the thermodynamics of quasi one-dimensional conductors, and are applied to experimental data for ${\mathrm{K}}_{0.3}$Mo${\mathrm{O}}_3$. These fluctuations are found to affect strongly the magnetic susceptibility and electronic entropy and heat capacity over a large temperature range.

Periodic structure is observed in the tunneling current from heavily doped ($n^{+}$) GaAs through ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ into lightly doped ($n^{-}$) GaAs at 1.6 K in magnetic fields large enough for magnetic freezeout of electrons to occur in the $n^{-}$-GaAs. Sixteen periods are observed for $-0.6\mathrm{}\mathrm{V}<V_G<0\mathrm{}\mathrm{V}$. The phase and the voltage periodicity, 0.036 V, are independent of magnetic field. The mechanism appears to involve LO-phonon emission events by ballistic electrons. This is the first observation of sequential single-phonon emission observed in electron transport.

The disorder parameter $k_{\mathrm{F}}l$ for amorphous $\mathrm{In}{\mathrm{O}}_x$ is measured by a novel application of the surface electric field effect and is varied by thermal annealing. The normal-state conductivity and superconducting $T_c$ both vary as ${\left(k_{\mathrm{F}}l\right)}^{-2\mathrm{}}$ and critical disorder occurs at $k_{\mathrm{F}}l\approx 3^{\frac{1}{2}}$, as a result of Anderson localization in this low—carrier-density material.

The $〈110〉$ directional total Compton profile of copper metal has been measured by inelastic scattering of 412-keV $\gamma$ radiation with special care for the multiple-scattering correction. The discrepancy between local density-functional band-structure calculations of the Compton profile and the experiment is attributed to a correction density functional, which clearly displays features due to nonlocal exchange-correlation effects.

The dynamic structure factor, $S(\overrightarrow{\mathrm{q}},\omega )$, of single-crystal Li exhibits a strong anisotropy of peak position and peak dispersion. For $q>\mathrm{}{q}_c$ ($q_c$ is the plasmon cutoff vector), at least the anisotropy of one peak position in $S(\overrightarrow{\mathrm{q}},\omega )$ can be attributed to zone-boundary collective states within the limits of a one-reciprocal-lattice-vector model. Therefore, the double-peak structure of $S(\overrightarrow{\mathrm{q}},\omega )$ for $q>\mathrm{}{q}_c$ seems not to be a universal property of the strongly correlated electron gas.

Longitudinal magnetoresistance measurements of hollow Mg cylinders between 1.5 and 10 K are reported and analyzed within the framework of weak electron-localization theories. The observed resistance oscillations decrease with increasing cylinder diameter and temperature, in excellent agreement with the theory of Altshuler et al. The phase-breaking and spin-orbit-interaction times are comparable to the values obtained in plane Mg films.

Long-range scattering of slow electrons by phonon excitations at flat and clean Cu(100) and Ni(100) surfaces has been observed in high-resolution electron-energy-loss measurements. We show that the strength of this electron-phonon coupling derives from the oscillatory response of the electrons at the metal surface. We have evaluated the electron-scattering cross section within the jellium model for the electron response and find excellent agreement with the experimental results.

The chemical structure of Si(111) exposed to a low coverage of oxygen has been investigated via Auger-electron spectroscopy. We have shown that the irradiation of an adsorbed monolayer of oxygen, by a weak laser beam at $\lambda =248\mathrm{}$ nm, induces important bond rearrangements at the Si(111) surface. This results in a disorderly structured monolayer of oxide, which relaxes into stable $a$-Si${\mathrm{O}}_2$ when heated up to $T_c\sim 949$ K.