The electronic structure of the Cu(100) surface has been calculated self-consistently. The calculation predicts a strong surface-state/surface-resonance band near the top of the bulk Cu $d$ band which has not been observed in previous calculations. The large attenuation in the experimental photoemission signal at the top of the $d$ band which is independent of photon energy and which occurs when various species are chemisorbed on Cu(100) is attributed to disturbance of this surface-state band by the chemisorbed atoms.

Nearly stoichiometric ${\mathrm{V}}_3$Si single crystal have been found to exhibit a double superconducting transition which in this instance is believed to be a fundamental physical feature representing an intermediate case between transforming and nontransforming material. A correlation between the existence and degree of the structural transformation and departure from stoichiometry in the Si-rich direction has also been observed.

We have observed 34 events with visible strange-particle production out of a total charged-current sample of 4500 events in a wide-band neutrino exposure of the Brookhaven National Laboratory 7-ft bubble chamber filled with ${\mathrm{H}}_2$ or ${\mathrm{D}}_2$. Three events were uniquely identified as having single-strange-particle production, two with $\Delta S=-\Delta Q$. In both $\Delta S=-\Delta Q$ events we observe the ${{\Lambda }_c}^{+}\mathrm{}\left(2260\right)\mathrm{}$, which in one case decays to $\Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-}$ and in the second case to $p{\overline{K}}^0{\pi }^{-}{\pi }^{+}$. Production rates are given.

This work offers a method for finding some exact soliton solutions to coupled relativistic scalar field theories in 1+1 dimensions. The method can yield static solutions as well as quasistatic "charged" solutions for a variety of Lagrangians. Explicit solutions are derived as examples. A particularly interesting class of solutions is nontopological without being either charged or time dependent.

We calculate diffractive production in nucleon-nucleus collisions using a parton model. We fit the result by the standard optical-model formula, and obtain estimates of 12-30 mb for the cross section of the diffractively produced system on a nucleon. The actual value of that cross section in the model is 65 mb. Estimates for the total cross section of an unstable hadron which are based on the $A$ dependence of coherent production should therefore not be trusted.

The cross section for production of ${\rho }^0$ mesons has been measured in the reaction $e+p\to e+p+{\pi }^{+}+{\pi }^{-}$. The cross section is presented as a function of $W$, the c.m. energy of the virtual-photon-proton system, and -$Q^2$, the square of the virtual-photon mass. The vector-dominance model is not able to describe the dependence of the cross section on the parameters $Q^2$ and $W$. The slope parameter $B$ describing the scattering of the proton exhibits a significant variation with $Q^2$.

It is shown that the total reaction cross section appropriate to the optical potential for scattering of a projectile by a target of uncorrelated particles (nucleons) can be written to a good approximation as a sum of exclusive cross sections for $n$-nucleon knockout. The association made by some authors of the reactive content of this optical potential with single-nucleon knockout is shown to apply to the inclusive-reaction cross section only.

In a generalization of the modified liquid-drop model obtained by requiring that two semi-infinite slabs of constant-density nuclear matter have minimum energy at zero separation, we calculate the generalized nuclear surface energy by means of a double volume integral of a Yakawa-plus-exponential folding function. This leads to a unified nuclear potential that is useful for describing heavy-ion elastic scattering and fusion, nuclear fission, and nuclear ground-state masses and deformations.

Excitation functions were redetermined for the reactions ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}$(${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$,$5-6n$) ${}_{}{}^{153-152}{}_{}{}^{}\mathrm{Er}$ and ${}_{}{}^{74}{}_{}{}^{}\mathrm{Ge}$(${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$,$5-6n$) ${}_{}{}^{153-152}{}_{}{}^{}\mathrm{Er}$, at two accelerators. Data obtained at the two accelerators agree. The new energy values are, however, different from those published earlier, and no significant differences occur between the (Ar,$\mathrm{xn}$) and (Kr,$\mathrm{xn}$) reactions leading to the same product nucleus. Thus, special mechanisms, such as pre-equilibrium neutron emission and angular-momentum windows, are not needed to interpret the new data.

The parities of four bound $J=1\mathrm{}$ levels in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ that are strongly excited by $\gamma$ rays were determined by observing the elastic scattering of plane-polarized photons. The levels at 5.51, 7.06, 7.08, and 7.33 MeV are excited by electric dipole radiation, and therefore have negative parity. The $1^{-}$ assignment for the 7.06-MeV level is of particular significance because this level had previously been thought to contain about 36% of the $M1$ strength in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$.

We report the first direct measurement of the effective initial tipping angle ${\theta }_0$ in superfluorescence. A coherent pulse of small area $\theta$, resonant on the superfluorescence transition, is injected into a completely inverted sample of cesium atoms and the delay of the out-put pulse is measured as a function of $\theta$. The value of ${\theta }_0$ obtained agrees in essence with $\frac{2}{{\mathrm{}\left(N\right)\mathrm{}}^{\frac{1}{2}}}$. The latter value is predicted by recent theories which consider the quantum initiation of superfluorescence and which take propagation effects into account.

Measurements and calculations are presented of reconnection and tearing of magnetic fields in a theta pinch operated with initial bias and driving fields in opposite directions. Open magnetic field lines reconnect and form magnetic islands on time scales of the order of an Alfvén transit time across the plasma sheath. Implications of these results for plasma confinement are discussed.

Compression of DT-neon-seeded, glass microballoons has been observed in C${\mathrm{O}}_2$-laser experiments at Los Alamos Scientific Laboratory. DT densities of the order of 20% of liquid density have been attained. Detailed comparisons of the neon densities determined from the measured neon source size and from the fit of observed spectra by Stark-broadening calculations have been made. The excellent agreement obtained with these methods indicates that the extrapolation of the microfield effects used in Stark-broadening calculations to high densities is reasonable.

Temporally resolved x-ray spectra in the range of 1-20 keV have been obtained from laser-irradiated high-$Z$ disk targets. We obtain the first time-resolved direct observation of the suprathermal x-ray tail resulting from hot-electron generation due to collective processes. The measurements indicated that the suprathermal temperature ${\theta }_H$ has a temporal behavior which essentially follows the laser pulse of intensity $I$, implying a relation ${\theta }_H\sim I^n$, $n\gtrsim 1$, an unexpected result.

A two-component, flux-limited diffusion model is introduced for the self-consistent transport of hot electrons in laser-produced plasmas. Megagauss fields from the $\nabla n_h\times \nabla n_c$ source are predicted for $I{\lambda }^2\gtrsim 3\times {10}^{16}$ W μ${\mathrm{m}}^2$/${\mathrm{cm}}^2$. For low-$Z$ target materials a prompt back-side $B$ field is a signature for hot electrons reaching the back of thin foils.

The precipitous onset step of Kosterlitz, Thouless, and Nelson has been investigated in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^4{}_{}{}^{}\mathrm{He}$ mixture films over the temperature range 1.3 K to $T_{\lambda }$. The constant relating the minimum value of superfluid density to the absolute temperature is found experimentally to be universal up to 30% ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. Comparison is made with recent mixture theories. Measurements were made at 24 MHz with a quartz microbalance adsorptometer.

High-energy ion scattering in combination with channeling has been used to study the W(001) + hydrogen surface. It is shown conclusively that the clean W(001) and the $\mathrm{W}\mathrm{}\left(001\right)c(2\mathrm{}\times 2)\mathrm{H}$ surfaces are reconstructed at room temperature, that the surface reorders by H saturation, and that two models proposed for the $c(2\mathrm{}\times 2)$ surface structure are not valid. Furthermore we have obtained absolute coverage data [for the W(001) + ${\mathrm{D}}_2$ system] using a nuclear reaction technique.

Saturation of the 9.4-GHz hypersonic attenuation was observed in crystalline quartz after fast-neutron irradiation. The sample, which exhibits long-range order, shows a low-temperature acoustic behavior similar to that observed in amorphous materials. As in glasses, the results can be explained by the existence of configurational low-energy excitations, with a two-state nature, which were put forward as intrinsic to the amorphous state.

The vibrational frequency-dsitribution spectra of the random one-dimensional ternary alloy $A_c{B}_{1-c}C$ are accurately predicted for the first time by a statistical theory of small clusters embedded in a coherent-potential-approximation effective medium. The theory can be applied practically to real three-dimensional alloys.

Using superconducting-quantum-interference device magnetometry, we have made the first direct measurement of the macroscopic quadrupole field which arises from antiferromagnetic order.