Isobaric-analog-state transitions have been observed throughout the periodic table in the (${\pi }^{+}$,${\pi }^0$) reaction. The forward-angle differential cross sections at $T_{\pi }=98\mathrm{}$ MeV on targets of C${\mathrm{H}}_2$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ are reported. The $A$ dependence follows $\mathrm{}(N-Z)\mathrm{}{A}^{-\frac{4}{3}}$, which is qualitatively understood in terms of a strong-absorption model. Optical-potential calculations which demonstrate the sensitivity to neutron density distributions and to the isospin dependence of higher-order dynamical effects are discussed.

This Letter reports observations showing that the spectral line shape in the core region of collision-broadened lines contains a dispersion component in addition to the usual Lorentzian. The physical origin of this component is the finite duration of the collisions. For the Na $D$ lines and Xe perturbers, the dispersion component produces an 8% asymmetry 0.1 Å from line center. Calculations based on recent line-broadening theories predict a dispersion component with an amplitude comparable to our experimental results.

A linear three-dimensional instability mechanism is presented that predicts Reynolds numbers for transition to turbulence in plane channel flows in good agreement with experiment.

The dynamics of envelope solitons accompanied by density depressions (cavitons) is analyzed with use of the driven Zakharov equations for inhomogeneous plasmas. The new contributions due to ion inertia as well as the novel phenomenon of amplitude-width-symmetry breaking are discussed. The results are applied to resonance absorption processes in laser-produced plasmas.

With use of molecular-dynamics techniquė for the classical Toda lattice, phonon, soliton, and second-sound excitation branches have been found.

It is shown that ${\mathcal{L}}^1$-clustering equilibrium states of classical systems of point particles are translationally invariant.

Renormalization-group techniques are applied to Ising-model spins placed on the sites of several self-similar fractal lattices. The resulting critical properties are shown to vary with the (noninteger) fractal dimensionality $D$, but also with several topological factors: ramification, connectivity, lacunarity, etc. For any $D>~1$, there exist systems with both $T_c=0\mathrm{}$, and $T_c>0\mathrm{}$; hence a lower critical dimensionality is not defined. The nonvanishing values of $T_c$ and the critical exponents depend on all these factors.

A truly unified model of the basic gauge interactions, except for gravity, based on the exceptional group $E_8$ is proposed. The fundamental fields belong to the smallest possible single representations for each spin. In addition to accounting for the three "observed" SU(5) families, this Letter predicts the existence of three more conjugate SU(5) families below 1 TeV.

Prompt dimuon production has been measured. Events with mass up to 25 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$ are observed, as well as the $J$ and $\Upsilon$ resonances. Cross sections are given for $J$ and $\Upsilon$ production. For the continuum, the scaling function $F\left(\tau \right)$ is measured at very small values of $\sqrt{\tau }=\frac{m}{\sqrt{s}}$ covering the range $0.05<\mathrm{}\sqrt{\tau }<0.20\mathrm{}$.

The forward-backward asymmetry of the normal to the event plane for $e^{+}{e}^{-}$ annihilation into three jets in higher-order perturbation-theory ($>~{{\alpha }_s}^2$) quantum chromodynamics is calculated. This could serve to establish the non-Abelian gluon self-couplings.

Inelastic electron scattering at large momentum transfer but small energy loss is used to investigate the high-momentum components in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. The data also show a striking scaling dependence in the variable $y=\overrightarrow{\mathrm{k}}·\frac{\overrightarrow{\mathrm{q}}}{q}$.

Exclusive ${\pi }^{-}$ and charged-particle production in collisions of Ar+KCl is studied at incident energies from 0.4 to 1.8 GeV/u. Complete disintegration of both nuclei is observed. The correlation between ${\pi }^{-}$ and total charge multiplicity shows no islands of anomalous pion production. For constant numbers of proton participants the ${\pi }^{-}$ multiplicity distributions are Poissons. For central collisions $〈n_{{\pi }^{-}}〉$ increases smoothly and to first order linearly with the c.m. energy. Disagreement with the firestreak model is found.

A previous assignment of the 21-ns isomer ${}_{}{}^{190}{}_{}{}^{}\mathrm{Hg}$ as ${{\left(\pi h_{\frac{11}{2}}\right)}_{{10}^{+}}}^{-2\mathrm{}}$ is investigated by means of a $g$-factor measurement. The experimental $g$ factor, -0.21±0.02, determines the configuration of the isomer as ${\left(\nu i_{\frac{13}{2}}\right)}^2$ and suggests a renewed study of the level scheme of ${}_{}{}^{190}{}_{}{}^{}\mathrm{Hg}$.

The differential cross section for the reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($p$,$p^{\prime }$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$* (15.11 MeV, $1^{+}$, $T=1\mathrm{}$) has been measured at 800 MeV; the range of the angular distribution corresponds to momentum transfers of 0.7-2.4 ${\mathrm{fm}}^{-1\mathrm{}}$ [$\mathrm{}(1-3.3)\mathrm{}{m}_{\pi }$]. The cross section decreases almost exponentially at large angles; no maximum is observed in the region where nuclear critical opalescence might be expected.

A search was made for a resonant, final-state interaction between carbon ions produced in the reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ → $\alpha$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ → $\alpha$ + ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$+${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ at $E_{\mathrm{lab}}=140\mathrm{}$ MeV. However, the $\alpha$-${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ coincidence spectra for both ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ targets were instead found to be dominated by the excitation and subsequent $\alpha$ decay of states in the projectile.

The effect of electric fields of up to 22 kV/cm on the absorption cross sections of argon and krypton have been obtained near the ionization limit. In both gases the field-induced cross section below the limit is found to represent the predicted oscillator-strength distribution. In krypton, additional field-induced fine structure appears below the limit.

The "pseudo-multipolar field," proposed by Jørgensen and Judd to account for hypersensitivity, is here applied to the ${}_{}{}^3{}_{}{}^{}H_4^{}{}_{}{}^{}\to {}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ transition of ${\mathrm{Pr}}^{3+}$. It is shown that the $2^6$- and especially the $2^4$-polar components give remarkable contributions, and cannot be neglected as has been done.

$K$ x rays produced in the bombardment of gas jet targets of helium, oxygen, and argon by sulfer and titanium beams have been measured for projectile charge states of +6 to +16 and +8 to +19, respectively. Unexpectedly, the charge-state dependence is similar for nearly symmetric systems and for very asymmetric systems. The results suggest that direct Coulomb excitation into empty bound states could be a common $K$-shell-vacancy production mechanism.

An analysis is presented of the steady states of two-dimensional convection in a laterally finite rectangular container near threshold. It is shown that the presence of sidewalls severely restricts the allowed wave vectors which can occur in the bulk of the container. This effect provides a possible mechanism to explain the observed wavelength increase of convective rolls with increasing Rayleigh numbers.

The two-dimensional nonlinear interaction of two planar ion-acoustic solitons has been studied experimentally. When the angle between the wave vectors of the two interacting solitons is small and the soliton amplitudes approach a critical value, a resonant three-soliton interaction occurs.