Nonlinear electrical conductivity associated with a large noise voltage has been observed in the semiconducting charge-density-wave state of the blue bronze ${\mathrm{K}}_{0.30}$Mo${\mathrm{O}}_3$. A well defined and strongly temperature-dependent threshold field for the onset of the nonlinear conductivity is found. Both broadband noise and quasiperiodic noise are detected above the treshold field. These results, including the observation of long relaxation times, are discussed in relation with the current models for charge-density-wave transport.

The existence of a new kind of electron state in graphite and in alkali graphite intercalation compounds is predicted with use of self-consistent local-density all-electron theory. These interlayer states, which exhibit free-electron character parallel to the layers, form a band close to the Fermi energy and provide for alkali graphite intercalation compounds a new understanding of the origin of bands previously interpreted incorrectly as arising from alkali $s$ electrons.

The influence of an electric field $F$ on the nature of electronic states in a one-dimensional disordered Kronig-Penney model is studied. By study of the Poincaré map of the Kronig-Penney model in a field, the transmission coefficient $T$ was calculated as a function of system size $L$. $T$ is found to behave as $L^{-\alpha \mathrm{}\left(F\right)\mathrm{}}$, with $\alpha \sim \frac{1}{F}$, for small $F$ which indicates power-law localization. In this regime, it is predicted that the resistance $R\left(F\right)\mathrm{}\simeq R\left(0\right)\mathrm{}(1-b|F\left|\right)\mathrm{}$, which may be checked experimentally.

Photoelectron spectra from ordered CO on Cu(111) exhibit anomalously small $4\sigma$ band dispersion compared to all other CO adsorption systems previously studied. The bonding $5\sigma$ band displays normal one-electron dispersion. It is shown that the energy dependence of the $4\sigma$ band expected for a single-particle system is transferred into $k$-dependent intensity variations of the quasiparticle excitation and the intense satellite line ∼2 eV lower in energy. The first moment of the spectral weight function over this energy range recovers the anticipated one-electron band dispersion.

Raman-scattering experiments from the commensurate charge-density-wave lattice modes of $2H$-Ta${\mathrm{Se}}_2$ exhibited large relative intensity variations as the incident polarization was rotated in the basal plane of the crystal. The observations are consistent with orthorhombic symmetry and imply the existence of either large (≈ 1 mm), or smaller coherently ordered, orthorhombic domains. A microscopic theory incorporating intralayer interactions with orthorhombic symmetry, in conjunction with an explicit proposal for the electronically active commensurate charge-density-wave regions, is also presented.

Picosecond pulse-excited photoconductivity measurements in a model disordered solid have provided direct evidence that triplet-exciton fusion is the precursor to free carrier formation and that the effective rate constant ${\gamma }_{\mathrm{eff}}$ of the fusion process is strongly dependent on the electric field, being driven from annihilation-rate limited at low field (∼ ${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^3$/sec) to nearly migration-rate limited (< ${10}^{-9\mathrm{}}$ ${\mathrm{cm}}^3$/sec) at high field. This field dependence is distinct from and in addition to that normally associated with the Onsager process.

It is shown that multicomponent fermion systems, with appropriate internal symmetry, can exhibit collective excitations with $D{q}^2$ dispersion at small $q$. Such a possibility is investigated for the four electron pockets in heavily doped $n$-type germanium.

Carbon is in widespread use as a first wall material for fusion experiments. Recent reports on the existence of a strong synergistic effect, when carbon is bombarded simultaneously by atomic hydrogen and electrons, create concern over this use of carbon. Such an effect could result in an unacceptably high chemical erosion of the walls and detrimental release of impurities into the plasma and fuel recycling system. Contrary to these reports, the authors have observed only a weak synergistic effect when carbon samples were strongly baked and the experiments performed in a specially cleaned UHV system.

Expanding the Dirac resolvent around its nonrelativistic limit, the authors propose a new method for calculating relativistic corrections to bound-state energies. The present results are more powerful than the expressions obtained by Foldy and Wouthuysen and remain applicable for Coulomb as well as nonlocal interactions.

Measurements of ion cyclotron-resonance frequencies in a Penning trap, by a laser fluorescence technique, are described. This technique has been applied to indirect measurements of the proton-to-electron mass ratio and the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}_{}^{+}{}_{}{}^{}$ electron $g_J$ factor. It is found that $\frac{m_p}{m_e}=1836.152\mathrm{}38\left(62\right)\mathrm{}$ (0.34 ppm) and $g_J\left({}_{}{}^9{}_{}{}^{}\mathrm{Be}_{}^{+}{}_{}{}^{}\right)=2.002\mathrm{}26206\left(42\right)\mathrm{}$ (0.21 ppm). Ultimately, ion cyclotron-resonance accuracies near 1 part in ${10}^{13}$ should be possible.

The object of this Letter is to show that except in the case of canonically conjugate observables, the generalized Heisenberg inequality does not properly express the quantum uncertainty principle. It is, in general, too weak. An inequality is obtained which does express the principle.

An exact solution of the eigenvalue problem $\{-\frac{d^2}{d{x}^2}+\Delta [1-a_0\rho \mathrm{}\left(x\right)\left]\right\}{\psi }_n\mathrm{}\left(x\right)=E_n{\psi }_n\mathrm{}\left(x\right)\mathrm{}$ with $\rho \mathrm{}\left(x\right)={\Sigma }_{n=1\mathrm{}}^N{\left|{\psi }_n\mathrm{}\right(x\left)\right|}^2$ and with periodic boundary condition is presented. The solution gives rise to a density wave with [const-$\rho \mathrm{}\left(x\right)\mathrm{}$] proportional to $\mathrm{s}{\mathrm{n}}^2\left[\right(\frac{x}{\lambda }\left)\right|m]\mathrm{}$ for suitable values of the parameters $\lambda$ and $m$. The solution rests upon some remarkable properties of the solutions of Lamé's equation.

The change in total energy-momentum of $N$ classically scattering charged point particles is shown to equal a flux integral depending on the asymptotic retarded fields of the particles. This flux integral is the energy-momentum flux of the electromagnetic field if the charges scatter according to the Lorentz-Dirac equation. All integrals are finite.

The authors prove, by considering a simple, exactly solvable model, that quantum systems under external perturbations may display a chaotic motion analogous to the corresponding classical ones.

The cross section for exciting simple atoms by slowly moving magnetic monopoles is calculated. Including the effects of the monopole magnetic field on the atomic energy levels, an energy loss per unit density is obtained that is much larger than previous studies. For helium $\left(\frac{1}{\rho }\right)\frac{\mathrm{dE}}{\mathrm{dx}}=15\left(\frac{\beta }{{10}^{-4\mathrm{}}}\right){[1-{(9.29\mathrm{}\times \frac{{10}^{-5\mathrm{}}}{\beta })}^2]}^{\frac{3}{2}}$ MeV ${\mathrm{cm}}^2$/g for $\beta$ in the range ${10}^{-4\mathrm{}}$ to ${10}^{-3\mathrm{}}$. The possibility of using helium as a monopole detector is discussed.

Bound states of the two-delta system are investigated by employment of the realistic oneboson exchange potential. It is found that there exist many bound states in each isospin channel and also that the tensor interaction plays an important role in producing these bound states. The relationship between these bound states and dibaryon resonances is discussed.

The authors have searched for the decay of protons and neutrons bound in nuclei using Soudan 1, a 31.5-metric-ton iron-loaded concrete tracking calorimeter, instrumented with 3456 proportional tubes. During a live time of 0.38 yr, the authors have observed one candidate event wholly contained within the detector. If this event is attributed to a background source, a lower bound (90% confidence level) can be established on the lifetime for nucleon decay through any of a wide range of modes of 1× ${10}^{30}$ yr.

The underground Soudan-1 nucleon decay experiment can measure the velocities of slowly moving particles if they can be detected by ionization at a level 0.5 times that of a relativistic muon. Magnetic monopoles predicted by grand unified theories should satisfy this condition if their velocities are greater than ${10}^{-3\mathrm{}}c$. During a live time of 0.41 yr, no candidate has been observed, implying a 90%-confidence-level limit on the flux of such objects of <4.1×${10}^{-13\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ for velocities between ${10}^{-3\mathrm{}}c$ and ${10}^{-2\mathrm{}}c$.

The polarization of magnetic states by $\Delta \mathrm{}\left(1232\right)\mathrm{}$-hole admixtures has been suggested as a possible mechanism to explain missing magnetic strength. Charge-exchange reactions on neutron excess targets may populate $2\hslash \omega$ spin-isospin flip states which have small hadronic form factors at low momentum transfers. Since the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ admixture produces ground-state-like form factors, an enhancement of the cross section at extreme forward angles is expected.

Backward stimulated Raman scattering measurements have been used to measure the frequency shift of the 992-${\mathrm{cm}}^{-1\mathrm{}}$ vibrational ring-stretching mode of benzene shock-compressed to pressures of 0.6 to 1.2 GPa. Results of the dynamic experiment are compared to shifts measured for benzene isothermally compressed with a diamond-anvil cell. A Grüneisen mode $\gamma$ was determined for this vibrational degree of freedom.