Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spindensity scheme. The theory explains the variation of the atomic volume and the bulk modulus through the $5f$ series in terms of an increasing $5f$ binding up to plutonium followed by a sudden localization (through complete spin polarization) in americium.

We present the analytical solution of the time-dependent Onsager problem, and show that above a critical value of the electric field the long-time behavior of the distribution function changes from diffusionlike to purely exponential. The possibilities of observing the effect experimentally are discussed briefly.

Starting from Hopfield's theory of the excitonic polariton, the energies and momenta of the particles involved in a two-photon Raman scattering process may be calculated self-consistently from the direction of the exciting photons, their energy, and the direction of the scattered light. Attributing to the calculated momenta the measured energies of the emitted photons, one obtains the dispersion relation of the excitonic polaritons with a high accuracy in a semiexperimental way.

We show that a first-principles nonlocal pseudopotential theory, based on an all-electron density-functional formalism, provides an essentially exact topological separation of both the octet $A^N{B}^{8-N}$ structures and the suboctet $A^N{B}^{P-N}(3\mathrm{}<~P<~6)$ structures for 77 and 56 non-transition-metal compounds, respectively. These pseudopotentials which also yield accurate descriptions of atomic and bulk solid electronic structure have been computed for 68 transition and nontransition elements.

We present direct thermodynamic measurements of the work functions ($\varphi$) of bound multiexciton complexes in Al-, B-, and P-doped Si. We find that the value of $\varphi$ differs in a number of cases from those obtained by assuming ground-state to ground-state transitions for some of the lines seen in luminescence. All the measured values of $\varphi$ are found to be less than the work function for the electron-hole liquid.

To explain the $\Upsilon -{\Upsilon }^{\prime }$ mass splitting of the recently discovered $\Upsilon$ resonances, we interpret them as bound states of a quark and an antiquark which are not members of the fundamental (3) representation of color SU(3). A quark in the 8 or 6 representation is consistent with the data. We discuss some of its properties and the phenomenological consequences that follow from our suggestion.

Selective-adsorption transitions have in the past been identified with minima in the intensity of specular reflection of atomic beams. New observations show that maxima can also occur, in excellent agreement with the recent theory of Weare and co-workers.

Liquid scintillators loaded with indium up to 200 g/l have been made to study the feasibility of detecting solar neutrinos by the ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$ inverse $\beta$ reaction scheme of Raghavan. To evaluate the background contribution due to the natural $\beta$ decay of ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$, we have measured its $\beta$ spectrum and find $T_{\frac{1}{2}}=4.41\mathrm{}\left(25\right)\mathrm{}\times {10}^{14}$ y and $E_{\mathrm{endpoint}}=482\mathrm{}\left(15\right)\mathrm{}$ keV. A direct counting indium detector of solar neutrinos appears feasible and possible configurations for such an experiment are briefly discussed.

We have measured high-$p_T$ ${\pi }^0$'s and jets with a two-arm calorimeter detector. Pions produce large-$x_T$ jets more readily than do protons. We report the first direct measurement of two-arm jets. We find that the jet pairs have roughly balanced $p_T$ and that pions produce jet pairs at more forward angles than do protons. These results give evidence for a constituent-scattering model, with constituents of higher average momentum in the pion.

We have measured inclusive electron production in multiprong events produced by $e^{+}{e}^{-}$ annihilation in the center-of-mass energy range 3.9-7.4 GeV. We find the electron momentum spectra are consistent with the electrons coming mainly from decays of charmed particles, with a smaller contribution from decays of the $\tau$ lepton. From our data we calculate the average branching ratio for charmed particles to decay into an electron plus additional particles to be (8.2±1.9)%.

Starting from an operator eikonal formula, we develop a new formalism which enables us to prove that, in quantum electrodynamics, a particle becomes completely absorptive at high energies.

A wide variety of final states are explored in the baryon exchange reactions ${\pi }^{-}d\to \left(p_s\right)X^{--}{p}_{\mathrm{forward}}$ and ${\pi }^{-}d\to \left(n_s\right)X^{-}{p}_{\mathrm{forward}}$, with a sensitivity of 240 events per microbarn per nucleon. We find no statistically significant evidence for charge -2 exotic mesons or any other new structure over a mass range extending from below the nucleon-antinucleon threshold to about 3.2 GeV.

I propose a test for the existence of stable or unusually long-lived neutral heavy leptons using a beam-dump experiment with precise timing. The technique can also be used to measure the lepton mass. Several reactions which can help to determine the couplings of such a lepton and can serve as new probes of hadronic structure are discussed.

A schematic model is used to calculate isospin-mixing from charge-dependent matrix elements derived from mass differences of isobaric multiplets. The model reproduces isospin-mixing matrix elements and trends observed in isospin-forbidden particle decays.

The rate at which the first nuclear excited state becomes populated is calculated as a function of temperature and compression for ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$.

Energy spectra and yields of $Z=1\mathrm{}$ particles from bombardment of an iron target with 192-MeV ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ ions were measured at a number of angles between 8° and 65°. The spectra extend to energies far above the energy per nucleon of the incident projectile. The observed yields are consistent with an interpretation that projectilelike products of the nuclear collisions are excited sufficiently to evaporate one or more light particles subsequent to the collision.

Cross sections for the electroexcitation of the ground-state rotational band in ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ have been measured over the momentum transfer range $0.5<~q<~2.5$ ${\mathrm{fm}}^{-1\mathrm{}}$ and are compared to calculations based on the variation-after-projection, Hartree-Fock approximation. The data support the predicted predominance of $\overrightarrow{\mathrm{L}}·\overrightarrow{\mathrm{S}}$ coupling for this band. The 5464-keV level is unambiguously identified as the ${\frac{7}{2}}^{+}$ member of the ground-state band.

It is shown that in the Stark quenching of a spin-polarized beam of metastable hydrogenic ions, a measurable right-left asymmetry can be produced in the emitted radiation which is proportional to the degree of spin polarization. The effect, which has previously been observed in absorption in neutral cesium and thallium, is due to interference between spontaneous magnetic dipole and induced electric dipole decay modes. Asymmetry measurements offer a simple means of determining the degree of spin polarization in the heavier hydrogenic ions.

Cross sections of processes ${\mathrm{Kr}}^{++}$+Kr → ${\mathrm{Kr}}^{++}$+Kr and ${\mathrm{Xe}}^{++}$+Xe → Xe+${\mathrm{Xe}}^{++}$ were measured by the injected-ion drift-tube technique from 0.04 to 20 eV. For both cases, the cross section below 1 eV coincides with the orbiting cross section with a charge-transfer probability ½. Above 1 eV, the energy dependence of the cross section is like that for single charge transfer. Mobilities of ${\mathrm{Kr}}^{++}$ and ${\mathrm{Xe}}^{++}$ in He are presented also.

We report observation of modulations in superradiance, resulting from the beating of light fields emitted by two groups of atoms with different velocities. The beat note is displayed from atomic frequency by the Doppler shift corresponding to the velocity difference (red or blue shift, depending on the direction of superradiant emission). Similarly many-atom beats should occur in superradiance from a mixture of different isotopes. Implications in spectroscopy are considered.