A large resonance in the photodetachment spectrum of metastable ${\mathrm{He}}^{-}$, which was recently predicted theoretically, has been observed experimentally. Located at 1.2344 eV with a width of 7.0 meV, the detachment cross section reaches a maximum of ∼70 ${\mathrm{\AA }}^2$. Its size results from the large oscillator strength associated with the first allowed transition in ${\mathrm{He}}^{-}$, $\mathrm{}\left(1s2s2p\right)\mathrm{}{}_{}{}^4{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}\to \left(1s2p2\mathrm{}{p}^{\prime }\right){}_{}{}^4{}_{}{}^{}P_{}^e{}_{}{}^{}$.

The dielectronic recombination cross section (${\sigma }^{\mathrm{DR}}$) was computed for the ${\mathrm{C}}^{1+}$ target ion in the region of continuum electron energies $9.0 \mathrm{eV}<~e_c<~9.3 \mathrm{eV}$. Since ${\sigma }^{\mathrm{DR}}$ exhibited many very sharp peaks, each of width < 0.001 eV, it was smoothed, for display purposes, by convolving with a square profile function of width 0.010 eV. The resulting smoothed cross section (${\overline{\sigma }}^{\mathrm{DR}}$) had values between ${10}^{-18\mathrm{}}$ and ${10}^{-17\mathrm{}}$ ${\mathrm{cm}}^2$.

Positronium negative ions ${\mathrm{Ps}}^{-}$ are formed by a beam of 420-eV positrons impinging on a thin carbon film in vacuum. Measurements of the number of ions reaching a grid under different acceleration conditions are used to determine both the ${\mathrm{Ps}}^{-}$ decay rate $\Gamma =2.09\mathrm{}\left(9\right)\mathrm{}$ ${\mathrm{nsec}}^{-1\mathrm{}}$ and its initial kinetic energy $T={13}_{-10\mathrm{}}^{+19\mathrm{}}$ eV. The decay rate is in good agreement with a recent calculation by Ho.

The experimental ion-yield curve for photoionization of atomic chlorine from the ionization threshold (∼ 956.1 Å) to 750 Å is reported. Three autoionizing series converging to the ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ ionic state and two series converging to the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ state are observed. The results are compared to existing many-body calculations.

Extreme ultraviolet Aliii line radiation at 56.0433 nm from a laser-produced plasma is used to optically pump a nearly coincident transition at 56.0437 nm in Cii produced in a vacuum arc. Time-resolved measurements of the resultant Cii ultraviolet fluorescence at 213.8 nm revealed up to a factor-of-8 increase in fluorescence, coincident with the Al laser-produced plasma.

Model mode-coupling equations for the resistive drift-wave instability are derived and numerically solved to study the properties of turbulence near a plasma edge. The wavenumber spectrum of the turbulence is found to exhibit an inverse cascade to form an isotropic, two-dimensional Kolmogorov spectrum, $k^{-3\mathrm{}}$, in the large-wave-number regime. The turbulence has a broad frequency spectrum with a large saturation level and produces Bohm-type particle diffusion.

The first renormalization-group approach for irreversible growth models of randomly branched aggregates is presented. The main result is that the Witten-Sander diffusionlimited aggregation model, a discrete version of a dendritic growth model, is in a different universality class than "equilibrium" lattice animals. Also calculated is the fractal dimension for the Witten-Sander model and the Eden model (a model developed for the study of biological structures).

A self-consistent theory for static and dynamic properties of planar magnets including quantum and correlation effects is presented. The renormalization and damping of the potentially soft mode is calculated. A central peak absorbing the spectral weight near the transition temperature is found. Qualitative agreement is obtained with observations made on Pr, which approximately represents a singlet-doublet model. The correlation theory is a systematic generalization of the random-phase approximation with an equally wide range of applicability.

A scaling theory for the interacting disordered fermion problem is constructed by extending the perturbation in coupling constant to second order. A scaling hypothesis produces a set of scaling equations which incorporates both localization and interaction. The resulting exponents are compared with experiments and further experimental tests of the theory are proposed.

A generalization of the virial theorem is presented for all components of the average stress tensor of arbitrary systems of interacting particles. Explicit expressions are given for local-density-functional calculations and the method is tested by ab initio pseudopotential calculations on silicon. Accurate determinations are made of lattice constant, bulk moduli, second-, third-, and fourth-order elastic constants, and the internal strain parameter $\zeta$. Agreement with experiment is very good, except for $\zeta$.

Quantum statistics can be reconciled with such classical ideas as distinguishable particles. Bose-Einstein and Fermi-Dirac statistics are derived for distinguishable particles by making an assumption regarding probabilities which is different from the traditional assumption but equally reasonable.

It is shown that eigenvalues of two-dimensional angular momentum remain integer valued in the magnetic field of a solenoid, contrary to published assertions that they are modified by the flux. For a vortex, flux does contribute, and the angular momentum can fractionize, as asserted in the literature, provided phases of wave functions are chosen consistently with the solenoid problem. Long-range effects of flux, the distinction between orbital and canonical angular momentum, and interactions with Cooper pairs are essential to this argument.

When a series of aluminum slabs are placed in one leg of a perfect-silicon-crystal neutron interferometer, a continuous and significant loss of contrast is observed. This observation is interpreted as being due to the finite length of the neutron wave packets.

The proposition that the coherence length of de Broglie wave packets remains unchanged even though the length of the packets increases upon propagation is discussed and demonstrated.

Using dioctyl-phthalate-doped CR-39 plastic track detectors with charge resolution ${\sigma }_Z\approx 0.06e$, the authors have made the first dynamic search for fractionally charged particles bound to nuclei. They find, from charge measurements in the first ∼ 2 cm after production, that no more than 3 × ${10}^{-3\mathrm{}}$ (95% confidence level) of the projectile fragments of 1.85-GeV/u ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ interactions with $10<~Z<\mathrm{}18\mathrm{}$ have charges differing from an integer by as much as $0.3e$. This rules out explanations of anomalons based on models in which the anomalons have nonintegral charge in such charge range.

Recent experiments at SLAC show unexpectedly large values for the ratios (1) $\frac{B(\psi \to \rho \pi )}{B({\psi }^{\prime }\to \rho \pi )}$ and (2) $\frac{B(\psi \to K^{*}\overline{K})}{B({\psi }^{\prime }\to K^{*}\overline{K})}$. It is proposed that these anomalies are caused by the mixing of the ground-state isoscalar vector mesons ($\omega , \varphi , \psi$) with a $J^{\mathrm{PC}}=1^{--}$ vector glueball ($O$) which was first postulated by Freund and Nambu in 1975. Its mass is estimated at ≃ 2.4 GeV and direct experimental searches for the $O$ are suggested.

An array of plastic scintillation counters was used to search for slowly moving, weakly ionizing particles between April and September 1982. The electronically defined velocity acceptance was $1\times {10}^{-4\mathrm{}}c$ to $3\times {10}^{-2\mathrm{}}c$. The sensitivity of the 2.7-${\mathrm{m}}^2$-sr detector was gradually increased until the threshold reached about $0.12I_{min}$. The decrease of scintillator excitation with velocity very likely introduced a lower velocity cutoff near $1.4\times {10}^{-4\mathrm{}}c$. The flux limit for the high-sensitivity runs corresponds to an aperture-solid-angle-time product of ${(5\mathrm{}\times {10}^{-12\mathrm{}}{\mathrm{cm}}^{-2\mathrm{}}{\mathrm{sr}}^{-1\mathrm{}}{\mathrm{s}}^{-1\mathrm{}})}^{-1\mathrm{}}$.

The neutron polarization for the reaction ${}_{}{}^2{}_{}{}^{}\mathrm{H}(\gamma , n_{\mathrm{pol}})\mathrm{H}$ was measured with high accuracy at an angle of 90° and in the photon energy range 6 to 13 MeV. The results were found to be in disagreement with present theoretical predictions which include meson-exchange currents.

Classical trajectories and semiclassical eigenvalues are calculated for an atomic Rydberg state in a magnetic field. Perturbation theory describes a classical trajectory as a Kepler ellipse which rocks, tilts, and flips in space as orbital parameters evolve slowly in time. Exact numerical calculations verify the accuracy of perturbation theory for $n\simeq 30$, $B<~6$ T. Action variables are calculated from perturbation theory and from exact trajectories, and semiclassical eigenvalues obtained by quantization of the action. Good agreement is found with observations.

The effect of turbulent electron diffusion from stochastic electron orbits on the stability of low-beta fluctuations is considered. A set of coupled self-adjoint equations is derived for the fluctuation potentials $\tilde{\varphi }$ and ${\tilde{A}}_{\parallel }$. For the tearing mode, it is shown that stability is obtained for sufficiently large values of the diffusion coefficient. Provided $D_e\sim \frac{1}{n}$, this implies that a density threshold must be surpassed before the tearing mode is observed. Numerical calculations also support this conclusion.