The photoproduction of the charmed baryon ${\Lambda }_c$ is reported. Clear signals are observed in the $p{K_S}^0$ and $\overline{p}{K_S}^0$ decay modes. The observed mass is 2284±5 MeV/${\mathit{c}}^2$ with a cross section times branching ratio of 3 nb/nucleon.

The polarization of 26 000 ${\Sigma }^{+}$ hyperons produced by 400-GeV protons on Be has been measured. The polarizations of ${\Sigma }^{+}$ and $\Lambda$ hyperons have the opposite sign. The magnitude increases with momentum at 5-mrad production angle, and averages 22% over the momentum range 140 to 280 GeV/c.

Exact axially symmetric multimonopole solutions of arbitrary topological charge are presented and their relevant features discussed.

A marked difference of ($p$,$t$) analyzing powers for the two isotones in $N=52\mathrm{}\to N=50\mathrm{}$ ground-state transitions was observed between two reactions, ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$($p$,$t$) and ${}_{}{}^{94}{}_{}{}^{}\mathrm{Mo}$($p$,$t$). The difference is not explained by direct one-step processes but is interpreted by including strong two-step ($p$,$d$) ($d$,$t$) processes. Interference between the two processes of comparable intensities is essential. Drastic incident-energy dependence of the analyzing powers is also interpreted only by including the two-step processes.

The widths of the momentum distributions for quasielastic fragments produced by ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ on ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at 20 MeV/amu and below are found, in contrast to a previous similar measurement, to be much smaller than at 2 GeV/amu. This contradicts a rapid change of reaction mechanism near 20 MeV/amu, in particular, the sudden onset of fragmentation or the decay from a nonequilibrated high-temperature subsystem.

Computations based on the full water-wave equations reveal that there are two distinct types of instabilities for gravity waves of finite amplitude on deep water. One is predominantly two dimensional and is related to all the known results for special cases. The other is predominantly three dimensional and becomes dominant when the wave steepness is sufficiently large.

Experimental data are presented which show that increased bandwidth of an electromagnetic driver can reduce the hot-electron temperature due to resonant absorption. This work, done at microwave frequencies, shows that $T_H\propto {\left(\frac{\Delta \omega }{\omega }\right)}^{-0.25\mathrm{}}$. We also observe that the hot-electron density increases with increasing bandwidth such that the heat flux ($Q_H\propto n_H{T_H}^{\frac{3}{2}}$) is nearly constant as a function of bandwidth.

Saturation mechanisms of free-electron lasers are investigated in the Compton regime. It is found that saturation occurs because of quasilinear energy spreading of the electron beam in the case of multimode excitation. The energy conversion efficiency remains low even if many modes are taken into account. To improve the conversion efficiency, the effect of reacceleration by a microwave is investigated and turns out to increase the efficiency to more than 50%.

The propagating shear wave ("second sound") in a smectic-$A$ liquid crystal was detected by an acoustic shear impedometric technique. The anisotropy of shear-wave velocity was determined, for the first time, in its entirety. The viscous-damped nature of the mode for propagation parallel and perpendicular to the normal to the smectic layer was also determined. The results confirm the predictions of the elasto-hydrodynamic theory of the smectic-$A$ liquid crystal.

Laser-induced fluorescence has been used to measure the rotational-state distribution of nitric oxide scattered from clean, single-crystal silver. Each resulting distribution is described by a rotational temperature within the statistical uncertainty. As the surface temperature is increased from 475 to 615 to 720 K, the calculated rotational temperature varies from 360±50 to 430±90 to 405±60 K, respectively. This shows that not only is rotational accommodation incomplete, but the degree of accommodation may decrease at the highest surface temperature studied.

Measurements of the low-temperature thermal expansion of $\gamma$-irradiated rubies have been made with use of a three-terminal capacitance dilatometer. The data exhibit a positive Schottky-type anomaly at ∼3.9 K, not present in the data obtained for a pure ${\mathrm{Al}}_2$${\mathrm{O}}_3$ sample, and this contribution to the thermal expansion has been tentatively attributed to the presence of ${\mathrm{Cr}}^{2+}$ (produced by $\gamma$ irradiation) exhibiting a large positive magnetic Grüneisen coefficient as predicted by a dynamic Jahn-Teller model.

A predictive relation between reacted interface width and heat of interface reaction is presented for III-V—compound-semiconductor-metal interfaces. Soft-x-ray photoemission measurements reveal that the thickness of chemically reacted species and the extent and stoichiometry of atomic interdiffusion are determined by the strength and nature of metal-semiconductor bonding. Chemical bond strength directly influences the macroscopic electronic properties as shown by transport measurements.

The relationship between the van der Waals description of the binding of rare-gas atoms to metal surfaces and the description using a local approximation for exchange-correlation effects is discussed. The local-density treatment is shown to provide a good account of recent data on atomic binding energy, dipole moment, and core-level binding-energy shift. Charge rearrangement maps are used to analyze bond formation and to discuss the validity of the image picture of core-hole screening.

The Landau-Ginzburg-Wilson model associated with the random alloy ${\mathrm{Fe}}_{1-x}{\mathrm{Co}}_x{\mathrm{Cl}}_2$ is analyzed. It is observed that the model includes a coupling term which has thus far been overlooked. Renormalization-group calculations in $d=4-\epsilon$ dimensions suggest that the multicritical behavior of this system is not associated with the "decoupled" fixed point found in previous theories. This prediction is consistent with recent experiments. A microscopic mechanism which generates this term is considered. It is suggested that similar terms may appear in other quenched alloys.

The excitation spectra of carbon $1s$ core electrons into the empty conduction-band states of polyacetylene and polyacetylene doped to saturation with As${\mathrm{F}}_5$ show that the electronic structure of the heavily doped samples is not that of a degenerate semiconductor, but rather that of a simple metal in which the original semiconducting band gap has been closed.

Evidence for superconductivity in the organic conductor di-(tetramethyltetraselenafulvalenium)-perchlorate [${\mathrm{}\left(\mathrm{TMTSF}\right)\mathrm{}}_2$Cl${\mathrm{O}}_4$] has been found by resistance measurements in the absence of applied pressure. For different crystals the transitions are approximately 0.3 K wide and are centered around temperatures between 1.2 and 1.4 K. At 0.9 K, a perpendicular magnetic field of 25 mT nearly restores normal resistance. Below 0.1 K, this critical field exceeds 50 mT.

The effect of configuration crossover on excited $4f^6\left({}_{}{}^7{}_{}{}^{}F_J^{}{}_{}{}^{}\right)$ levels has been investigated by electronic Raman scattering in ${\mathrm{Sm}}_{1-x}{\mathrm{Y}}_x\mathrm{Se}$ and ${\mathrm{Sm}}_{1-x}{\mathrm{Y}}_x\mathrm{S}$. The multiplet levels are wiped out when they merge with the conduction band, or when interacting with phonons. Polarized Raman-scattering data on ${\mathrm{Sm}}_{1-x}{\mathrm{Y}}_x\mathrm{S}$ for $x>\mathrm{}0.15\mathrm{}$ show that the contribution from $J$-multiplet levels is unobservable and that the peak near 250 ${\mathrm{cm}}^{-1\mathrm{}}$ arises from optic phonons and not from $J=0\mathrm{}\to J=1\mathrm{}$ excitations.

The information contained in an Auger-electron-photoelectron coincidence spectroscopy (AEPECS) experiment for $\mathrm{XXV}$, $\mathrm{XYV}$, and $\mathrm{XYZ}$ Auger processes when a single $X$ level is involved is discussed. For finite systems AEPECS gives information about the spatial character of the excited states, while for a system with a continuous spectrum AEPECS provides no additional information when the Auger lifetime is long.

For the first time, both specific heat and susceptibility have been measured in a system which spans the entire mixed-valence range in a continuous manner. Ce ions in $\mathrm{Ce}{\left({\mathrm{Pd}}_{1-x}{\mathrm{Rh}}_x\right)}_3$ and $\mathrm{Ce}{\left({\mathrm{Pd}}_{1-y}{\mathrm{Ag}}_y\right)}_3$ go from tetravalent ($n_f=0\mathrm{}$) for $x>~0.20$ to trivalent ($n_f=1\mathrm{}$) for $y>~0.13$. Both $\gamma$ and $\chi \mathrm{}\left(0\right)\mathrm{}$ increase dramatically as $n_f$ varies from 0 to 1. Comparisons to theories are presented.

The ion emission from a field-produced Taylor cone on a molten tin surface is found to consist of many atomic and molecular species, the abundance of which is analyzed by mass spectroscopy. The energy spectra for these different ions have been measured for several emission currents, providing information about the mechanism of ion production. The behavior of the energy spread is discussed in terms of Coulomb interactions in the beam.