Measurements of the trapping of positrons in $\beta$-brass have shown that the vacancy formation energy dramatically increases with the ordering of the alloy below the order-disorder transition temperature. Based on predictions from our trapping-model analysis of the monovacancy behavior, we have searched for, and found above 430°C, direct evidence for the cusp-shaped rise in the trapping of positrons by divacancies that is characteristic of the rapid growth in the thermal divacancy population as the order parameter goes to zero.

A surface-plasmon-mediated absorption mechanism is proposed to explain the measured frequency dependences of both the optical conductivity and infrared mass of smooth sodium surfaces.

Optical detection of magnetic resonance is reported for the blue donor-acceptor pair luminescence in $6H$-SiC containing nitrogen and aluminum. The nitrogen donor resonance is isotropic, with $g=2.004\mathrm{}\pm 0.002$. Resonances for the aluminum acceptor in three inequivalent silicon lattice sites are detected with $g_{\parallel }=2.412\mathrm{}\pm 0.002, 2.400\pm 0.002, \mathrm{and} 2.325\pm 0.002$; and $g_{\perp }=0\mathrm{}$. This indicates an effective-mass-like character for the acceptor, but with reduced orbital contribution due to the localization. Evidence for corresponding reduction in the spin-orbit splitting is cited.

The properties of an electron in a disordered solid are discussed with use of a matrix nonlinear $\sigma$ model first introduced by Wegner and Schäfer. The model is defined on the noncompact space $\frac{\mathrm{O}\mathrm{}(M,M)\mathrm{}}{\left[\mathrm{O}\mathrm{}\right(M)\mathrm{}\times \mathrm{O}\mathrm{}(M\left)\right]}$ where $M$ is the number of replicas. This noncompact symmetry represents the assential physics of the problem. It is found that all states are localized in two dimensions; above two dimensions for weak disorder there are mobility edges, but these merge above a critical amount of disorder and all states become localized.

The $L_{23}$ near-edge fine structure has been investigated in electron-energy-loss spectra from thin films of $3d$ transition metals and an unexpected departure from the statistical $\frac{L_3}{L_2}$ "white-line" intensity ratio of 2: 1 is reported. For Ti, a ratio of 0.7: 1 is observed, while for Fe and Ni the ratio exceeds 3: 1, indicating a systematic trend within the period. It is suggested that many-electron effects may be important.

In the long-wavelength limit, $\Gamma ({\psi }^{\prime }\to \gamma +{\chi }_J)=\mathrm{const}\times \mathrm{}(2J+1)\mathrm{}{p_{\gamma }}^3$ and $\Gamma ({\chi }_J\to \gamma +\psi )=\mathrm{const}\times {p_{\gamma }}^3$. The corrections to these expressions of order $\frac{p_{\gamma }}{m_c}$ ($m_c$ is the mass of the charmed quark) are calculated. These corrections are found to be proportional to ${〈\overrightarrow{\mathrm{L}}·\overrightarrow{\mathrm{S}}〉}_{{\chi }_J}\times \kappa$, where ${〈\overrightarrow{\mathrm{L}}·\overrightarrow{\mathrm{S}}〉}_{{\chi }_J}=1,-1,-2\mathrm{}$, for $J=2,1,0\mathrm{}$, and $\kappa$ is the anomalous magnetic moment of the quark. Angular distributions of photons in the decays ${\psi }^{\prime }\to \gamma \chi$ and $\chi \to \gamma \psi$ also are predicted; small but probably measurable deviations from the pure $E1\mathrm{}$ limit are found.

A fourth state in the upsilon energy region has been seen in $e^{+}{e}^{-}$ collisions at the Cornell Electron Storage Ring. A resonance is observed with a mass 1112±5 MeV above the lowest upsilon state. The 9.6-MeV rms width is greater than the 4.6-MeV energy resolution of the $e^{+}{e}^{-}$ beams. The observed characteristics of the new state make it a likely candidate for the $4{}_{}{}^3{}_{}{}^{}S$ state of the $b\overline{b}$ system, lying above the threshold for the production of $B$ mesons.

During an energy scan at the Cornell Electron Storage Ring, with use of the Columbia University-Stony Brook NaI detector, an enhancement in $\sigma (e^{+}{e}^{-}\to \mathrm{hadrons})$ is observed at center-of-mass energy ∼10.55 GeV. The mass and leptonic width of this state (${\Upsilon }^{\prime \prime \prime }$) suggest that it is the $4{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ bound state of the $b$ quark and its antiquark. After applying to the data a cut in a (pseudo) thrust variable, the natural width is measured to be $\Gamma =12.6\mathrm{}\pm 6.0$ MeV, indicating that the ${\Upsilon }^{\prime \prime \prime }$ is above the threshold for $B\overline{B}$ production.

Dynamically broken gauge theories of electroweak interactions provide a natural mechanism for generating $\mathrm{CP}$ nonconservation. Even if all vacuum angles are unobservable, strong $\mathrm{CP}$ nonconservation is not automatically avoided. In the absence of strong $\mathrm{CP}$ nonconservation, the neutron electric dipole moment is expected to be of order ${10}^{-24\mathrm{}}$e·cm.

This Letter describes a topological bootstrap theory of strong interactions that generates baryon number, three topological "colors," and spin-½ confined "quarks" with eight flavors. Extension to electromagnetism allows the topological objects called "quarks" to be associated with leptons, so that eight leptons are predicted.

The electromagnetic form factor of the negative kaon has been measured by direct scattering of 250-GeV/c kaons from the stationary electrons of a liquid-hydrogen target The deviation of the measured elastic scattering cross section from the point cross section may be characterized by a root-mean-square kaon radius of ${〈{{\mathcal{r}}_{K^{-}}}^2〉}^{\frac{1}{2}}=0.53\mathrm{}\pm 0.05$ fm.

A simple three-quark Hamiltonian based on a quark-antiquark interaction which accurately describes all $q\overline{q}$ mesons has been solved numerically. Good agreement with the ground-state baryon mass spectrum is obtained if the $\mathrm{qq}$ and $q\overline{q}$ interactions differ by an overall factor of 2 as expected from an octet color-exchange mechanism. The interactions in a three-quark system appear to be very well described by only a sum of pair interactions.

Inelastic scattering of 800-MeV protons from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ shows a broad giant resonance at an excitation energy of $\frac{110}{A^{\frac{1}{3}}}$ MeV. The angular distributions are consistent only with scalar-isoscalar $l=3\mathrm{}$ transfer. The excitation energy and width of this high-energy octupole giant resonance are in reasonable accord with theory. However, its energy-weighted sum-rule strength (∼20%) is only about one half that predicted by randomphase-approximation calculations.

The fore-aft asymmetry in the angular distribution of the reaction ${}_{}{}^3{}_{}{}^{}\mathrm{H}$($p$,${\gamma }_0$)${}_{}{}^4{}_{}{}^{}\mathrm{He}$ has been measured as a function of energy for protons from 17 to 31 MeV. The same quantity was also measured using the reaction ${}_{}{}^4{}_{}{}^{}\mathrm{He}(e,{}_{}{}^3{}_{}{}^{}\mathrm{H})p{e}^{\prime }$. These asymmetry data were fitted with an expression which consisted of a term which varied slowly with energy plus a $2^{+}$ resonance having parameters of ${\Gamma }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=3.5\mathrm{}$ MeV and $E_x\left(\mathrm{res}\right)=40.2\mathrm{}$ MeV.

The electron-photon coincidence technique is used to separate the 54.4-eV electron impact $2p$ and $2s$ excitation cross sections of atomic hydrogen. The $\frac{2s}{2p}$ cross-section ratios, normalized to theory at 10°, are in excellent agreement with the close-coupling calculations of Kingston, Fon, and Burke, in reasonable agreement with hybrid pseudostate close-coupling plus unitarized Born calculations, but in strong disagreement with the distorted-wave Born-approximation and hybrid close-coupling plus distorted-wave polarized-orbital calculations.

A measurement of the $g_J$ factor of the hydrogenlike ion ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$ in its $1{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ ground state has been made using an optical pumping technique. This represents the first precision measurement of the $g_J$ factor of a simple atomic ion. The result is $\frac{g_J({}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{},1\mathrm{}{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{})}{g\left(e^{-}\right)}=1-70.87\mathrm{}\left(30\right)\mathrm{}\times {10}^{-6\mathrm{}}$. This value agrees with theory and provides confirmation of the Breit term $\frac{1}{3}{\left(Z\alpha \right)}^2$ to within 0.5%.

A numerical model is used to show that the range of suprathermal electrons from laser-produced plasmas can be significantly reduced by the electric field needed to drive a return current of cold electrons. Direct experimental evidence of a reduction of preheat by at least a factor of 3 is presented for targets containing a low-density gold layer.

A pure, fully ionized, ${\mathrm{D}}_2$ plasma of 2×${10}^{19}$ ions, generated from free-falling ${\mathrm{D}}_2$ pellets with use of a 100-J Nd-glass laser pulse followed by a 1000-J C${\mathrm{O}}_2$ laser pulse, is used to fill ($\beta =1\mathrm{}$) a cusp-configured magnetic field. The width of the plasma escaping through the ring cusp is determined by laser scattering, chamber wall light and chemical deposits, and plasma lifetime. The ring cusp is an ion gyroradius wide, in contrast to recent experiments that have indicated a considerably narrower cusp width.

The hypothesis of dynamical scaling asserts that, sufficiently close to the critical temperature, the decay rate $\Gamma$ of the order-parameter fluctuations assumes the form $\Gamma =q^z\Omega \left(q\xi \right)$, where $q$ is the wave number and $\xi$ the correlation length. A new accurate experimental study of this decay rate in 3-methylpentane-nitroethane yields the value 3.06 ± 0.02 for the dynamical scaling exponent $z$, in excellent agreement with the theoretical predictions for the dynamic universality class of fluid systems.

Results of zero-sound attenuation measurements in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$, at frequencies up to 60 MHz and pressures between 0 and 20 bars, are reported. At frequencies of 30 MHz and above, a new attenuation feature is observed which bears the signature of a collective mode of the superfluid.