The ($p, \gamma$) reaction populating highly excited states in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ is shown to be dominated by giant dipole resonances built upon one-particle, one-hole states. Each giant resonance is centered at $E_{\gamma }\approx 20$ MeV, with a width which increases with the energy of the one-particle, one-hole state, and with a strength that is simply related to the proton stripping strength to the same final state.

Observation of the $T+1\mathrm{}$ component of the isovector monopole and the giant dipole resonances in the reactions ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}({\pi }^{-}, {\pi }^0)$ at $T_{{\pi }^{-}}=165\mathrm{}$ MeV is reported. The isobaric analog state and $T-1\mathrm{}$ component of the giant dipole resonance in the reaction ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}({\pi }^{+}, {\pi }^0)$ were also observed. Excitation energies and widths of the monopole are given.

Studies of the first time dependence in Rayleigh-Bénard convection in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are reported. The aspect ratio $\Gamma$ could be varied continuously. Data at 31 $\Gamma$ values with $4<\mathrm{}\Gamma <13\mathrm{}$ show that near onset the first time dependence is always periodic and associated with changes in the heat transport. The dominant periodicity has a nonzero amplitude, $A$, and vanishing frequency at onset. Changes in $A$ with $\Gamma$ show wave-number effects. Except for the time dependence, the transition is consistent with predictions for the skew-varicose instability.

A potential depression is formed between two magnetized plasmas with different electron temperatures and ion species in the absence of electric current passing through them. The depression is deep enough to reflect both groups of electrons, reducing thermal contact between the plasmas. By addition of a magnetic bump to a uniform magnetic field, the potential dip is localized around the mirror point. A dependence of the phenomenon on neutral-gas pressure is also clarified.

The Andersen-Parrinello-Rahman constant-pressure molecular-dynamics technique has been generalized to study molecular crystals. The method, which appears to have wide applicability, is used to study structural transformations in solid nitrogen at high pressures.

Intense gain satellites associated with the $M_{2,3}\mathrm{VV}$ Auger transition have been observed for representative $3d$ transition metals. The satellites have line shapes and intensities that resemble those of the $M_{2,3}$ electron-energy-loss and resonant photon-excited spectra of these materials and are identified as being due to autoionization electron emission. This identification satisfies the expectation that the Fano effect should be manifest in both absorption and emission experiments, whether photon or electron excited.

It is shown that in contrast to band theory, a self-consistent one-electron model with broken symmetries (crystal orbitals are not constrained to be Bloch periodic) provides a physical description of core-ionization, core-exciton, and core-to-conduction-band transition energies in semiconductors. Application to GaP shows that a hitherto unrecognized factor—the screening of the core-hole self-energy by the electron orbit—can explain many of the outstanding puzzles in core-hole spectra.

The authors have diagonalized numerically the Hamiltonian of a two-dimensional system of up to six interacting electrons, in the lowest Landau level, in a rectangular box with "periodic" boundary conditions. They find that the ground state has a pair correlation function quite different from that of a Wigner crystal, and its energy is significantly lower. They also find some indications of a downward cusp in the energy at $\frac{1}{3}$ filling.

A novel interplay of coherent spatial structure and temporal chaos is reported for the acdriven, damped sine-Gordon system with breather initial conditions and periodic boundary conditions. The competing tendencies of spatial structures to be stable and of single-particle motions to be chaotic can lead to suppression of chaos, spatio-temporal intermillency, and symmetry-breaking tendencies. Dynamic structure factors provide direct evidence for spalial period halving and renormalized-phonon generation in chaotic regimes.

It is pointed out that at $N\to \infty$, for finite temperature, the Schwinger-Dyson equations imply that below the deconfining phase transition the Wilson loops are independent of the temperature. This suggests a first-order deconfinement phase transition.

The authors have measured the polarization of 2.4×${10}^5$ ${\Lambda }^0$ hyperons in inclusive production by 12-GeV protons on tungsten at three production angles, 3.5°, 6.5°, and 9.5°. In terms of Feynman's $x_{\mathrm{F}}$ and transverse momentum of ${\Lambda }^0$, the kinematical range is $0.3<~x_{\mathrm{F}}<~0.8$ and $0.4<~p_{\mathrm{T}}<~1.6$ GeV/c. The observed polarization does not depend strongly on $x_{\mathrm{F}}$ and increases linearly with $p_{\mathrm{T}}$ to 16% at $p_{\mathrm{T}}=1.0\mathrm{}$ GeV/c, showing a tendency to level off above that point.

An excitation function for the reaction ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}({\pi }^{+}, {\pi }^{-}){}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$ has been measured at ${\theta }_{\mathrm{lab}}=5\mathrm{}°$ for incident pion energies of 140-290 MeV. The transition to the lowest-lying $T=0\mathrm{}$ state is similar to previous observations, but that to the lowest-lying $T=2\mathrm{}$ state is not, except in the high-energy range.

By measuring the range deficit of 955-MeV/u ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ ions in copper, the authors have identified very large deviations of the stopping power from the standard Bethe-Bloch formula. They show that this discrepancy can be accounted for by higher-order terms in the Mott cross section and by the relativistic Bloch correction. The significance of this result with regard to two high-energy astrophysics experiments is discussed.

The angular asymmetry parameter $\beta$ for the Xe $5s\to \epsilon p$ photoelectrons has been studied with use of synchrotron radiation ($h\nu =28-65\mathrm{}$ eV). The present results show that the relativistic random-phase approximation theory does not satisfactorily describe the Xe $5s$ photoionization process close to the Cooper minimum and thus require a renewed theoretical approach. The $5s$ partial photoionization cross section was obtained over the same photon region and the results agree with experimental values found in the literature.

The exit channels in the region of the $3d\to 4p$ resonance of atomic gallium were determined in a photoemission experiment. The population of the three major channels involving $4p$ and $4s$ electrons was measured by the constant-ionic-state method for twenty resonant states between 18.8 and 21.7 eV, and the angular distribution of the emitted electrons was obtained. As a result, an autoionization case in which many resonances and many continua are coupled has been characterized in the most comprehensive experiment to date.

The phase speed of infinitesimal disturbances in a relativistic gas is shown to be less than the speed of light. The result is obtained by means of the kinetic theory of gases and is valid for any collision operator. The treatment applies, in particular, to the speeds of propagation of sound, shear, and heat waves. These waves are further shown to be damped.

The authors have measured the diffusion constants of aerosols whose size compares to the mean free path of the gas in three different aerosols. The experimental diffusion constants do not agree with the kinetic-theory calculations in this intermediate Knudsen regime.

The same physical mechanism which causes stimulated Brillouin backscattering of a laser pulse when interacting with the underdense plasma (in laser fusion systems) can be used to reverse the scattering direction in order to drastically reduce the reflectivity. Forced stimulated rescattering may be obtained by additional radiation pulses or by a multihumped spectrum with each peak down-shifted by twice the acoustic frequency. Analytical four-mode and numerical six-mode models show strong reduction of the reflectivity for the same input intensity.

The three-dimensional character of the beam-plasma instability is investigated. The true beam-electron distribution function is resolved with a novel directional energy analyzer. The electron plasma waves ($\omega \approx {\omega }_p\gg {\omega }_c$) are observed to develop a large spread in perpendicular wave numbers ($\delta k_{\perp }\approx k_{\parallel }$) and damp in a relatively short distance producing an energetic electron tail on the background distribution. The damping is believed to be due to strong ion fluctuations which produce an anomalous resistivity.

The presence of an inverted population of H↓ with very high electronic and nuclear spin polarization is confirmed with a new barometric-NMR method and by free-induction decay. With this new technique, the temperature dependence for the ratio of the two state-dependent recombination rate constants is measured. The rate of spin relaxation in the gas agrees with the latest theory, but relaxation on the surface is much faster than predicted, and there is an important surface one-body relaxation process.