We construct a threshold $K$ matrix for the dominant $\mathrm{PS}11\left(\epsilon N\right)$ contribution to ${\pi }^{-}p\to {\pi }^{+}{\pi }^{-}n$ that agrees with (1) the result of partial-wave isobar-model analyses above 1300 MeV, (2) the result of a single-arm-spectrometer experiment below 1300 MeV, and (3) the predictions of the effective Lagrangian at threshold. We find that the chiral-symmetry-breaking parameter $\xi$ is -0.2±0.3, and that by only 10 MeV above threshold, isobar production accounts for roughly one-third of the total cross section.

Results of experiments on the collective acceleration of H, He, N, Ne, Ar, and Kr ions with an intense relativistic electron beam (1.5 MeV, 30 kA, 30 ns) are reported. Using time-of-flight diagnostics, we found that the ion beam front velocity was approximately $v\approx 0.1c$ for each particle species. This corresponds to a maximum kinetic energy of 390 MeV for Kr.

Photon-echo measurements in atomic Na perturbed by He provide the first demonstration of the contribution of velocity-changing-like effects to the transverse relaxation of atoms in superposition of two states even when the states follow different post-collision trajectories. The apparent anomaly that broadening cross sections derived from either absorption line widths or photon-echo relaxation measurements are smaller than the total cross section for scattering of atoms in either pure state is explained.

Two sum rules for order-parameter susceptibilities are derived for the classical theory of the three-phase region near a tricritical point in ordinary liquid mixtures. The classical theory can also be fitted in a quantitative way to the composition data of Lang and Widom near the tricritical point in the mixture ethanol + benzene + water + ammonium sulfate.

Measurements of light-scattering intensity and correlation lengths in all three coexisting phases in the mixture water + benzene + ethanol + ammonium sulfate are reported for temperatures near the tricritical point. A comparison with two sum rules predicted by a classical theory shows fairly good agreement in one case and significant deviations in the other. Possible explanations of the latter are discussed.

The ultrasonic absorption and variation of the sound velocity have been measured in sputtered films of amorphous silicon and amorphous silicon oxide from 0.5 to 300 K at a frequency of 300 MHz. A Rayleigh surface wave propagating along the surface of a piezoelectric crystal, which is covered by a thin film of amorphous Si${\mathrm{O}}_2$, allows a measurement of the well-known acoustic anomalies originating from two-level tunneling systems. In clear contrast, films of $a$-Si do not exhibit these typical anomalies.

Polycrystalline aluminum samples have been irradiated with very short (15-ns time duration) pulses from a ruby laser. After irradiation, we have detected the formation at the Al surface of a noncrystalline layer, about 1500 Å thick. This layer has been characterized by transmission electron microscopy, x-ray diffraction, and nuclear reactions. Perliminary results are also presented on the behavior of heavily Cu- and Pb-doped Al polycrystalline samples after being irradiated under the same conditions as the pure Al samples.

A calculation of the bulk-plasmon-satellite strengths in the photoemission spectra of metals is presented for the dispersionless plasmon model. The calculation is made for all energies, especially for the ultrasoft-x-ray regime. In this spectral region, the interference term between extrinsic and intrinsic plasmon productions is of the same order as the intrinsic production term. The photoelectron energy for which these two terms cancel each other exactly is determined.

Using angle-resolved photoemission with single-crystal Fe(111) and Co(0001), we have determined accurate exchange-split energy-band dispersions $E\left(\overrightarrow{\mathrm{k}}\right)$ along symmetry lines. For Fe, Co, and Ni, respectively, occupied $d$-band widths are 3.1 eV ($P$), 3.8 eV ($L$), and 3.4 eV ($L, X$), while exchange splittings are ∼1.5 eV ($P$), ∼1.1 eV ($\Gamma$), and 0.3 eV (near $L$). Comparison with theory shows that state-of-the-art ab initio calculations describe the strong ferromagnets Fe and Co much better than Ni.

In amorphous, nongranular, thin films of ${\mathrm{Nb}}_3$Ge, the temperature dependence of the resistance and the current-voltage relation have been investigated at temperatures below the experimentally determined thermodynamic transition. This temperature-dependent resistance is compared to several theories which predict flux-flow resistance below the BCS transition temperature due to thermally excited vortex pairs.

Studies of the adiabatic order-parameter susceptibility near symmetry-breaking phase transitions show that the ratio $\frac{{\chi }_S\mathrm{}\left(t\right)\mathrm{}}{{\chi }_S\mathrm{}(-t)\mathrm{}}$ (in the limit $t\to 0^{+}$), and the proportion of the order-parameter spectral intensity associated with the thermal diffusion mode (in the limit $t\to 0^{-}$), are universal. The universal quantities are tabulated and discussed in the light of experiments on structural phase transitions, with particular emphasis on the dielectric properties of ferroelectrics and the scattering properties of ordered phases. New experiments are suggested.

A peak in the $p{K}^{-}{\pi }^{+}$ and $\overline{p}{K}^{+}{\pi }^{-}$ invariant-mass spectra at 2.285±0.006 GeV/${\mathit{c}}^2$ is observed, which is associated with the lowest-lying charmed baryon (${\Lambda }_c$). A cross section times branching ratio of 0.037±0.012 nb at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=5.2\mathrm{}$ GeV is measured with a substantial fraction of the events produced with an equal recoiling mass. New measurements of inclusive $p$ and $\Lambda$ cross sections are also presented, allowing an estimate of the branching ratio $B({\Lambda }_c\to p{K}^{-}{\pi }^{+})=0.022\mathrm{}\pm 0.010$.

For elastic scattering of 20-MeV polarized deuterons from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ we measured vector and tensor analyzing powers including $A_{\mathrm{xz}}\left(\theta \right)$. An optical-model analysis demands a tensor term of 13 MeV, which exceeds the folding-model value by a factor of 2.

A new approach based on the collective tube model is developed for understanding momentum transfer to target fragments in high-energy hadron-nucleus collisions. Collectivity manifests itself in an enhanced dependence of momentum transfer on projectile energy, consistent with experimental results for deep-spallation reactions. The effective target for ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tb}$ production from ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ by high-energy protons is deduced to consist of 3.1±0.4 nucleons. Extensions of this model to nucleus-nucleus collisions are discussed.

The ${}_{}{}^4{}_{}{}^{}\mathrm{He}(p, 2p){}_{}{}^3{}_{}{}^{}\mathrm{H}$ reaction has been measured at 250, 350, and 500 MeV using symmetric geometries. The energy dependence of the cross section at zero recoil momentum and angular distributions are presented. The data are compared to distorted-wave impulse-approximation (DWIA) calculations. Unlike at lower energies, the zero-recoilmomentum data are well described by the DWIA at these energies. For the angular distributions, the DWIA increasingly underestimates the data as the recoil momentum is increased.

Time-dependent Hartree-Fock fusion calculations are presented for head-on collisions of ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ + ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$ and ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}$ + ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$. A large fusion region is found for moderately high energies above the Coulomb barrier, and a lower limit for the fusion cross section of ${}_{}{}^{84}{}_{}{}^{}\mathrm{Kr}+{}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}\to {}_{119}{}^{293}{}_{}{}^{}X_{}^{*}{}_{}{}^{}$ is estimated from non-head-on collisions. Also, fusionlike behavior is found for a narrow range of energies near the barrier.

The role of isoscalar giant quadrupole excitations in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ as doorway states for symmetric fission and intermediate structure resonances in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ elastic scattering is investigated by means of model calculations using particle-hole excitations over two major shells. The fission mode is treated as a shape degree of freedom that couples the giant quadrupole resonances in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ to the ground state. The associated intermediate-structure resonances have calculated widths for symmetric fission and $\gamma$ decay that are in qualitative agreement with experiment.

With the use of crossed beams of electrons and multiply charged argons ions, dominant contributions (above 90%) of $L$-shell ionization to multiple ionization of ${\mathrm{Ar}}^{i+}$ ions ($i=1, 2, 3$) at electron energies below 800 eV are identified. The observed contributions are explained in terms of the electron rearrangement processes following $L$-shell ionization.

The resonant response of a stack of disks driven into torsional oscillation within a container of rotating superfluid helium has been observed. It is shown that the oscillation modes excited are related to Tkachenko waves, that is, vortex displacement waves in the vortex array propagating in a direction transverse to the vortex lines. In particular, the resonances occur at peaks in the vortex-wave density of states.

Surface phonons of metals at certain points of the two-dimensional Brillouin zone can be observed in electron energy-loss spectroscopy when suitable coupling is provided by commensurable adsorbate lattices.