Conditional probability distributions based on accurate wave functions for ${\mathrm{He}}^{**}$ confirm the proposal that electron correlation in doubly excited atoms leads to quantization like that of a linear triatomic molecule.

We suggest that group-theoretic techniques may be useful for studying two-electron correlations in atoms. We show that matrix elements of the Coulomb interaction for doubly excited states of the ${}_{}{}^1{}_{}{}^{}S$ configuration can be approximated by a constant plus a pairing term. The latter gives rise to a highly correlated state similar to a Cooper pair in the electron gas. It may be identified with the state that leads to the Wannier threshold law for the escape of two electrons from a Coulomb core.

We demonstrate that large rectangular fluid layers have several essentially time-independent convective states above the critical Rayleigh number $R_c$ in which the rolls align perpendicular to all lateral boundaries. The pattern is hence splayed and contains defects. Using real-time laser Doppler imaging, we show that the onset of time dependence at $R_1\cong 5R_c$ arises from a structural instability of the rolls which can be suppressed by a local heat source.

It has been verified experimentally that an intense, space-charge-neutralized ion beam having a dielectric constant $\epsilon \gg 1$ will cross a transverse magnetic field undeflected. A polarization electric field $\overrightarrow{\mathrm{E}}$ is measured within the beam channel such that $\overrightarrow{\mathrm{E}}+\left(\frac{\overrightarrow{\mathrm{v}}}{c}\right)\times \overrightarrow{\mathrm{B}}=0\mathrm{}$, where $\overrightarrow{\mathrm{v}}$ is the beam velocity and $\overrightarrow{\mathrm{B}}$ is the applied field. It is shown theoretically that $\epsilon \gg {\left(\frac{m_i}{m_e}\right)}^{\frac{1}{2}}$ is required for the beam to enter the transverse field from a region with no field, where $m_i$ and $m_e$ are the ion and electron masses.

Neutral-hydrogen-beam injection parallel to the plasma current (co-injection) has been observed to produce smaller concentrations of both naturally occurring and injected impurities than counter-injection. We explain this result by considering the effect of plasma rotation on radial impurity transport. This rotation effect could be the basis of an impurity-control technique for tokamak fusion reactors.

A self-consistent study of the partition of energy absorbed in nanosecond single-C${\mathrm{O}}_2$-laser-beam irradiation of glass microballoons is reported. Through interferometric inference of shell heating, and quantitative fast-ion spectrometry, it is shown that a major fraction of the absorbed energy is converted to fast-ion expansion and only 25% contributes to thermal heating of the target.

In laser-fusion applications the laser electric field can reach large values near the critical surface. We propose a method of determining the strength of these electric fields experimentally. The idea is to use the fact that an intense laser field splits bound-bound radiative transition lines into a band of lines, the width of the band depending on the laser intensity. By seeding a target locally with a low-$Z$ material it should be possible to obtain information on the strength of the laser electric field at different positions in the plasma.

Specific heat of the enhanced paramagnetic material palladium was measured in magnetic field up to 11 T. The fitted value of the electronic-specific-heat coefficient $\gamma$ was found to decrease from 9.36 mJ/mole ${\mathrm{K}}^2$ at zero field to 8.63 mJ/mole ${\mathrm{K}}^2$ at 11 T, but we did not observe a field dependence of the Debye temperature ${\theta }_{\mathrm{D}}$. We attribute our findings to the paramagnon effect in palladium.

Angle-resolved time-of-flight measurements of inelastic scattering of Ne atoms from a Ni(111) surface show an effective interaction radius increased with respect to the Ne hardsphere radius, such that the Ne atoms impact against five Ni atoms. This limits the interaction with acoustic surface waves to some critical cutoff wave vector, $K_c$. Larger energy transfers are accompanied by vanishing momentum transfer as assumed in a cubes model.

Nonlinear equations for zero sound interacting with the $B$-phase collective modes are derived by treating ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$ as a medium of two-level "molecules" (Cooper pairs). The nonlinear equations reduce to known results from kinetic theory in the linear response limit. Soliton solutions to the nonlinear equations are discussed in context with the experiments of Polturak et al.

The nonlinear $I-V$ characteristics below the superconducting transition of high-sheet-resistance Hg-Xe films have been analyzed with use of a model in which the nonlinearity is a consequence of current-induced vortex-antivortex unbinding. The characteristics can be fitted by $V\sim I^{a\left(T\right)\mathrm{}}$, where $a\left(T\right)\mathrm{}$ is a measure of the a real superelectron density $n_s\mathrm{}\left(T\right)\mathrm{}$. The universal relations predicted for the Kosterlitz-Thouless-Berezinskii transition in two dimensional superconducting films are obeyed.

We report new measurements of thermoreflectance spectra of Cr${\mathrm{Br}}_3$ in the paramagnetic and ferromagnetic phases in the 2.5-4 eV region. The spectra obtained with use of unpolarized and circularly polarized light, with and without external magnetic field, allow one to identify the dominating modulation mechanisms: electron-phonon interaction modulation (shift and broadening effects) in the paramagnetic phase, and exchange interaction modulation (splitting effects) in the ferromagnetic phase.

"Spin doping" by paramagnetic ions adds to the electronic $g$ factor of charge carriers in semiconductors, a temperature sensitive part, so that by means of the artificial temperature dependence any intraband resonance transition can be identified unambiguously.

A new type of compensated Penning trap with the ring electrode split into equal quadrants allows intense unshifted ion cyclotron resonances to be synchronously detected with very small relative linewidths (< 2×${10}^{-9\mathrm{}}$). By measuring the cyclotron frequencies of both protons and electrons in the same magnetic field (5 T) and the same trapping volume (<${10}^{-7\mathrm{}}$ ${\mathrm{cm}}^3$), a preliminary value of the mass ratio $\frac{m_p}{m_e}=1836.153\mathrm{}00\left(25\right)\mathrm{}$ is obtained with an accuracy that is more than four times greater than any previous direct measurement.

We prove the mathematical equivalence of Nambu-Goto strings to local scalar fields $S\left(x\right)\mathrm{}$ and $T\mathrm{}\left(x\right)\mathrm{}$ described by the Lagrangian $\mathcal{L}=-\int d^{4}x{\left\{\frac{{\left[\frac{\partial \mathrm{}(S,T)\mathrm{}}{\partial (x_{\mu },x_{\nu })}\right]}^2}{2}\right\}}^{\frac{1}{2}}$ Implications to the quantization problem of strings are also discussed.

Dine, Fischler, and Srednicki have proposed a solution to the strong $\mathrm{CP}$ puzzle in which the mass and couplings of the axion are suppressed by an inverse power of a large mass. We construct an explicit SU(5) model in which this mass is the vacuum expectation value which breaks SU(5) down to SU(3) ⊗ SU(2) ⊗ U(1).

We have observed the sharply resonant enhancement of the cross section of the collision process $ns+ns\to np+(n-1\mathrm{})p$ between two $\mathrm{Na}ns$ ($16<~n<~27$) atoms which occurs when the levels are shifted by an electric field so that the $ns$ level lies midway between the two $p$ states. The widths of the collisional resonances scale as $n^{-2\mathrm{}}$ and the magnitudes of the cross sections as $n^4$, with values of 0.5 GHz and 8×${10}^8$ ${\mathrm{\AA }}^2$ for the $20s$ state. These results are in good agreement with calculations based on the long-range dipole-dipole interaction between the two atoms.

We solve exactly the problem of double configuration mixing (Coulombic and radiative) in a "Fano model" atom, and predict a new confluence of coherences in laser-induced autoionized electron spectra.

We report an application of self-consistent pseudopotential Green's-function calculations to the problem of identification of defects in GaP. The results are in agreement with and support the EPR-based identification of the P antisite defect, but contradict the assumptions that led to the identification of the Ga vacancy. We reexamine other possibilities using the results of our calculations and find that C at Ga sites is the only center whose properties are consistent with the available data.

We have shown by displacement-sensitive high-energy ${\mathrm{He}}^{+}$-ion scattering that the clean Ni (111) surface has a bulklike structure with ∼20% enhancement of surface thermal vibration, and that the $p(2\mathrm{}\times 2)$ and $(\sqrt{3}\times \sqrt{3})R30°$ superstructures on the oxygen-adsorbed surface are accompanied by expansion of the first nickel layer by ∼0.15 Å. In addition, the absolute oxygen coverages for these two superstructures and at saturation were measured to be ∼¼, $\sim \frac{1}{3}$, and ∼3 monolayers, respectively.