An investigation has been made of the $l$-redistribution effect of quasistatic ion electric microfields on dielectronic recombination. Using the linear-Stark-effect approximation, a hydrogen ion density of ${10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$ is found to produce a threefold enhancement in the rate for the dielectronic recombination process ${\mathrm{Fe}}^{+23\mathrm{}}\mathrm{}\left(2s\right)+e^{-}\to {\mathrm{Fe}}^{+22\mathrm{}}(2p,nl)\to {\mathrm{Fe}}^{+22\mathrm{}}(2s,nl)+\hslash \omega$.

Large localized potential double layers, $e\varphi >>k{T}_e$, are observed to develop from a solitary $E$-field structure in a plasma traversed by electron drifts, $v_d\simeq v_e$. Strong electron and ion accelerations occur across the layers. At large electron drift velocities ($v_d>3\mathrm{}{v}_e$), layers are unstable to large ion fluctuations with $\frac{\delta n}{n}$ approaching unity.

A simple model is given for magnetic field generation by steep steady-profile wavefronts such as ablation waves or shocks propagating across initially field-free nonuniform plasmas or fluids. The model enables one to obtain approximate values for the field penetration through the ablation layer into the interior of a laser target or pellet. These fields could also be produced and measured in laboratory ionizing shock tubes.

Through Callan-Symanzik methods, the individual susceptibilities for the slow and fast components of an order parameter with two time scales are derived above $T_c$. For one-component fluids, a new experession for the Landau-Placek intensity ratio is found.

Electron-paramagnetic-resonance studies of the cooperative Jahn-Teller system Tm${\mathrm{VO}}_4$ doped with Gd indicate that in the high-temperature phase the behavior of the spectrum is probably dominated by the presence of random strains arising from the Jahn-Teller effect. The random strain effects in these systems have so far been largely neglected.

The Raman spectra of the layer-structure compounds $2H-\mathrm{Nb}{\mathrm{Se}}_2$ and $2H-\mathrm{Ta}{\mathrm{Se}}_2$ have been measured between 2 and 300 K. A low-energy peak in the Raman spectrum is found to soften at the charge-density-wave phase transition. This peak is attributed to the charge-density-wave amplitude mode. The intensity and energy of this soft mode have been successfully compared with mean-field treatments of the charge-density-wave phase transition.

Superconducting transition temperatures of $\mathrm{Hf}{\mathrm{V}}_2{\mathrm{H}}_x$ and $\mathrm{Hf}{\mathrm{V}}_2{\mathrm{D}}_x$ have been measured in the composition ranges $x=0-1.5\mathrm{}$ and $x=0-1.0\mathrm{}$, respectively. Hydrogen or deuterium absorption is found to decrease $T_c$ of ${\mathrm{HfV}}_2$. Pronounced isotope effects have been observed. At $x=1\mathrm{}$, hydrogen absorption reduces $T_c$ by 4.8 K while deuterium absorption reduces $T_c$ by 6.9 K with respect to ${\mathrm{HfV}}_2$.

Splitting of energy levels of atoms bound to a crystal surface have been observed in atomic beam scattering.

Doppler-broadending studies have been conducted on the $\gamma$ rays following annihilation of positrons in plastically deformed copper samples. Evidence for a temperature dependence of the trapping rate comes from the observation that in the sample investigated the fraction of positrons trapped varied by 30% in the range 6-77 K.

Recent experiments on silicon inversion layers in the activated conductivity regime have shown a variety of electronic behaviors which are in marked disagreement with the predictions of Mott-Anderson localization, which is due to random static-potential fluctuations. It is argued here that there is an additional mechanism causing electron localization which involves electron-pair states in the energy gap of the disordered oxide. It is shown that by including this mechanism it is possible to account for a variety of these electronic properties including the dependence of the mobility edge on electron density.

The broadening of the intrinsic absorption edge by intense, acoustoelectrically amplified phonon flux in piezoelectric semiconductors is well established. A definitive test is presented to show that the piezoelectric fields of the phonons in GaAs are predominantly responsible for this effect. The test consists of using intense extrinsic generation of excess electrons by a $Q$-switched, Nd-doped yttrium-aluminium-garnet laser to screen out the piezoelectric fields without affecting the acoustic intensity.

We have observed voltage-tunable far-infrared emission from inversion layers of $n$-channel metal-oxide-simiconductor field-effect transistors fabricated on $p$-type (100) Si. The radiation is emitted by the electronic transition from the two-dimensional excited-state $E_1$ sub-band of the inversion layer to its ground-state $E_0$ sub-band. Population of the excited-state sub-band is realized by heating up the electron distribution with an electric field applied along the channel.

Films consisting of fine Ni grains (∼50 Å) dispersed in ${\mathrm{SiO}}_2$ exhibit a large negative magnetoresistance. The effect is accounted for by the field dependence of the magnetic exchange energy, associated with tunneling of electrons between neighboring grains whose magnetic moments are not parallel.

Current theories of surface segregation are based on either the difference in the sizes or the heats of sublimation of the alloy components. We show that neither of these theories gives adequate agreement with experiment. A simple rule, based on the melting curve of the alloy, gives good agreement with all available experimental data.

We estimate renormalization effects on $\frac{{\sigma }_{\overline{\nu }}}{{\sigma }_{\nu }}$ and ${〈y〉}_{\overline{\nu }}$ in the standard four-quark model, improving on a calculation by Altarelli, Petronzio, and Parisi. Even with systematic overestimates, the Weinberg-Salam model does not give a satisfactory account of the data.

We present the characteristics of a model calculation of multimuon production in deepinelastic muon scattering. In the model the muons are assumed to originate from the production and subsequent weak decay of a pair of hadrons that carry new quantum numbers and have a mass of ∼1.8 GeV. The results of the calculation are to be compared with the forthcoming experimental data, and could shed light on the properties of the new hadrons.

We report measurements of the ratio of positively charged to negatively charged pions electroproduced at 0° and 90° in the virtual photon-nucleon center-of-mass system. The $\frac{{\pi }^{+}}{{\pi }^{-}}$ ratio is studied as a function of $W$, $Q^2$, $\omega$, $x_T$, and $x$ in the range $2.1 \mathrm{GeV}<~W<~3.2 \mathrm{GeV}$ and $1.2 {\mathrm{GeV}}^2<~Q^2<~9.5 {\mathrm{GeV}}^2$.

Using 13.5-GeV beams at Stanford Linear Accelerator Center, we have compared electron and positron inelastic scattering over the range $1.2<\left|q^2\right|<\mathrm{}3.3\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, $2<\mathrm{}\nu <9.5\mathrm{}$ GeV for the four-momentum and energy transfers, respectively. We find the ratio of the cross sections to be $\frac{e^{+}}{e^{-}}=1.0027\mathrm{}\pm 0.0035$ (including statistical and systematic effects), with no significant dependence on $q^2$ or $\nu$. This result has appreciably smaller errors than previous attempts to find two-photon-exchange effects in electron or muon scattering.

We report measurements of the exclusive electroproduction reaction $e+p\to e+{\pi }^{+}+n$ for pions produced near 0° in the virtual-photon-proton center-of-mass system with values of $\epsilon$ in the range $0.35<\mathrm{}\epsilon <0.45\mathrm{}$. Combination with data taken at $\epsilon$ near 1 allows us to separate the contributions from transversely polarized and scalar photons in the range $1.2 {\mathrm{GeV}}^2<Q^2<3.3\mathrm{} {\mathrm{GeV}}^2$.

A relativistic three-body theory of the ($2^{+}$) $\mathrm{NN}\pi$ system was applied to calculate elastic and inelastic $\left({}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}\right)\mathrm{pp}$ scattering below 1 GeV. Although the amplitude satisfies all standard resonance criteria, it has no pole corresponding to a diproton resonance.