It is shown that the limitation to the energy gain of $2{\left(\frac{\omega }{{\omega }_p}\right)}^{2}m{c}^2$ of an electron in the laser-plasma beat-wave accelerator can be overcome by imposing a magnetic field of appropriate strength perpendicular to the plasma wave. This accelerates particles parallel to the phase fronts of the accelerating wave which keeps them in phase with it. Arbitrarily large energy is theoretically possible.

This Letter examines the possibility of using spin-polarized DT fuel for inertial-confinement fusion. Analytic models and estimates are developed to determine whether an initial spin-polarized state would survive target irradiation and implosion. It is found that collisional depolarization cross sections are not large enough to give significant depolarization, and that the short duration of inertial-fusion implosions precludes spin resonance for magnetic fields that can be reasonably expected in the target fuel.

It is shown that in tokamaks with neoclassical banana-regime heat conduction and ion self-collisions dominant for energy scattering, the distribution tail diffuses outwards radially and downwards in energy maintaining a constant effective temperature ${\left(\frac{-\partial \ln f_i}{\partial \epsilon }\right)}^{-1\mathrm{}}$, as observed in some experiments.

The first study of the atomic structure of Si chalcogenide glasses is reported. The Raman spectra are remarkably simple and can be understood in terms of the vibrations of a bitetrahedral ${\mathrm{Si}}_2{\left(X_{\frac{1}{2}}\right)}_8$ ($X=\mathrm{S},\mathrm{S}\mathrm{e}$) unit. The present results represent the most compelling evidence for medium-range order and a molecular-cluster description of a compound amorphous semiconductor.

It has been demonstrated directly by use of x-ray diffraction that at temperatures below the triple point of bulk ethylene (103.8 K) adsorption of ethylene onto the basal planes of graphite only occurs up to a finite number of molecular layers. Further addition of molecules results in the formation of bulk crystallites. Reversible transitions between the total number of layers adsorbed and the coexisting bulk are observed.

A neutron-diffraction study of deuterated-ethylene overlayers on graphite basal planes reveals the existence of three distinct adsorbed solid phases as well as the coexistence of adsorbed and bulk phases at higher coverages. Evidence of a surface wetting transition involving transfer of molecules from the bulk to adsorbed phase is also obtained.

Single-phase ${\mathrm{Au}}_{1-x}{\mathrm{La}}_x$ alloys, with $0.3\lesssim x\lesssim 0.5$, have been formed through solid-state interdiffusion of pure polycrystalline Au and La thin films (100-600 Å) at temperatures of 50-80°C. The reaction is driven by the large negative heat of mixing in the amorphous alloy and occurs at low temperatures by the anomalously fast diffusion of Au in La. The composition regime giving a single-phase amorphous product is explained with use of a free-energy diagram.

Vibrational emission from molecular defects in ionic crystals has been observed for the first time, realized by dilute C${\mathrm{N}}^{-}$ defects in KCl which emit a long-lifetime fluorescence at 4.8 μm. After association of $F$ centers to the C${\mathrm{N}}^{-}$ defects, the emission can be pumped efficiently by optical $F$-center excitation through electronic-vibrational coupling. This coupling is confirmed through Raman experiments. Relative intensity, emission spectra, and lifetime data as a function of crystal temperature are reported for the 4.8μm emission.

The transient volume change of $\alpha$-quartz and fused silica induced by irradiation with an electron pulse has been measured above 80 K. It is shown that transient changes of volume and optical absorption due to the ${E_1}^{\prime }$ centers (oxygen vacancies) decay in parallel and that the volume change per ${E_1}^{\prime }$ center is of the order of a unit molecular volume. The results show unambiguously that recombination-induced defect formation occurs in Si${\mathrm{O}}_2$ but the defects created are not stable even at low temperatures.

The first observation of spin-dependent thermal emission from a deep gap state in a semiconductor is reported. As a result the silicon dangling-bond defects at the Si/Si${\mathrm{O}}_2$ interface can be directly correlated with a 0.36-eV-deep hole trap.

Angle-resolved inverse photoemission with tunable photon energies has been used to map out the unoccupied bands of graphite and lithium-intercalated graphite. At the Brillouin zone center the bottom of the lowest band is found at 4.0±0.5 eV above the Fermi level in graphite. This band shows strong dispersion normal to the basal plane in excellent agreement with recent self-consistent band-structure calculations. A similar three-dimensional band is found in lithium-intercalated graphite shifted 3 eV to lower energy.

The Kramers theory for the escape rate of a Brownian particle moving in a potential well is generalized to account for the full viscosity range. An expression for the escape rate, which is valid for all values of the friction and yields the Kramers results in the appropriate limits, is obtained.

The problem of determining the deviation $\delta V\left(\overrightarrow{\mathrm{r}}\right)$ of a local scattering potential $V\left(\overrightarrow{\mathrm{r}}\right)=V_0\left(\overrightarrow{\mathrm{r}}\right)+\delta V\left(\overrightarrow{\mathrm{r}}\right)$ from a known background potential $V_0\left(\overrightarrow{\mathrm{r}}\right)$ by use of scattered-field data is addressed within the distorted-wave Born approximation. A procedure is presented that allows $\delta V\left(\overrightarrow{\mathrm{r}}\right)$ to be approximately reconstructed from the potential's scattering amplitude $f(k\overrightarrow{\mathrm{s}},k{\overrightarrow{\mathrm{s}}}_0)$ assumed specified for fixed $k$ and all incident (${\overrightarrow{\mathrm{s}}}_0$) and observation ($\overrightarrow{\mathrm{s}}$) directions. The reconstruction method is shown to be a generalization of an inversion procedure developed earlier, to which it reduces when $V_0\left(\overrightarrow{\mathrm{r}}\right)\equiv 0$.

A new method based on the $S$-matrix factorization is developed for the thermodynamics of the massive Thirring model. The method can be applied to any charge sector and coupling constant. In the zero-charge sector, the present theory reproduces all the Bethe-Ansatz-theory results in the attractive-coupling regime, and agrees with a perturbation calculation in the repulsive-coupling regime.

A search for superheavy magnetic monopoles "catalyzing" nucleon decay via the reaction $M+N\to M+e^{+}+\mathrm{mesons}$ in an undergound water Cherenkov detector has been carried out. No positive evidence for such a process has been found during 100 d of detector live time. Cross section and velocity-dependent limits on the monopole flux are presented which are as low as $F_m<7.2\mathrm{}\times {10}^{-15\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ (90% C.L.). For very low cross sections, velocity-independent limits on the monopole flux and interaction rate are obtained.

The conserved-vector-current hypothesis, together with measured nuclear-beta-decay rates, predicts a value of the rate for the decay ${\pi }^{+}\to {\pi }^0{e}^{+}\nu$ of 0.4027±0.0018 ${\mathrm{s}}^{-1\mathrm{}}$. With use of a decay-in-flight technique the authors have made the most precise measurement to date of this rate, obtaining the value 0.398±0.015 ${\mathrm{s}}^{-1\mathrm{}}$, in good agreement with the prediction.

It is proposed that the dynamical contribution to the hadron electromagnetic mass difference induced by the splitting of the up and down quark masses can be extracted phenomenologically from the quark masses by interpolation, in accordance with general QCD assumptions. The results are consistent with all observed electromagnetic mass differences. The model-independent prediction $B^0-B^{+}=2.3\mathrm{}\pm 0.3$ MeV will serve as a crucial test for these assumptions. A useful mass formula for the $s$-wave hadron ground states is also presented.

The reactions $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}\gamma \gamma$ and $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}\gamma$ have been studied at $\sqrt{s}=29\mathrm{}$ GeV with the MAC detector at the SLAC storage ring PEP. The measured cross sections, charge asymmetry, and invariant-mass distributions are in good agreement with the predictions of QED theory. Limits are derived for the production of excited muon states.

Recent deep-inelastic lepton-scattering data from iron and deuterium targets are interpreted from a quark-model viewpoint as evidence for a significant number of six-quark clusters in iron. Standard expectations for the distribution of quarks within a six-quark cluster give some quantitative success in describing the data.

Large-amplitude magnetosonic waves ($\overrightarrow{\mathrm{k}}\perp \overrightarrow{\mathrm{B}}$) with ${\omega }_{\mathrm{ci}}<\omega <{\omega }_{\mathrm{lh}}$ (${\omega }_{\mathrm{ci}}$ and ${\omega }_{\mathrm{lh}}$ are the ioncyclotron and lower-hybrid frequencies) are investigated by particle simulation. Some ions are accelerated and trapped in the potential troughs of the waves; the $\overrightarrow{\mathrm{v}}\times \frac{\overrightarrow{\mathrm{B}}}{c}$ force accelerates these particles parallel to the phase fronts. Ultimately, the $\overrightarrow{\mathrm{v}}\times \frac{\overrightarrow{\mathrm{B}}}{c}$ force detraps the ions but only when $\overrightarrow{\mathrm{v}}$ is much larger than the Alfvén velocity; the wave is strongly damped by this effect.