Fission angular distributions for nuclei formed by fusion of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$, ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{248}{}_{}{}^{}\mathrm{Cm}$ show an appreciable anisotropy although spherical saddle-point configurations are predicted for these systems by the rotating-liquid-drop model. The analysis of the data in terms of the statistical model indicate that composite systems of $Z=106, 108, \mathrm{and} 112$ have been formed with deformations $\beta <~0.35$.

We have found that the shape of the potential for $4f$ electrons in Tm predicts quite well the character of the $4d\to 4f$ autoionization resonance observed in the photoelectron spectra. The direct photoemission from the $4d$ shell is suppressed by a barrier in the potential. Tunneling through this barrier is significantly slower than the decay of the excited electron back into the $4d$ hole. This decay is thus the dominant channel and is observed to lead predominantly to autoionization of the $4f$ shell.

By introducing a Doppler switching technique in collinear fast-ion—beam laser spectroscopy, transient interference phenomena were observed. The shape of the experimental spectra can be related to the Fourier analysis of the evolution in time of the laser frequency, as probed by the ions.

We report x-ray measurements on $\mathrm{Nb}{\mathrm{H}}_x$ single crystals, at high temperatures. In addition to the strong fundamental ($\mathrm{hh}0$) x-ray reflections, weak intensity peaks were observed at the $\frac{1}{2}\left(hh0\right)$ positions ($h$ odd). The intensity of these weak peaks increases with H concentrations. It is proposed that the experimental results come from periodic distortions of the Nb host lattice, in regions with partial ordering of hydrogen atoms in every second (110) plane, caused by pretransitional fluctuations of the low-temperature ordered $\zeta$-phase ${\mathrm{Nb}}_2$ H.

Standard x-ray diffraction in which a reflection goemetry is used is shown to have a simple interpretation and adequate sensitivity for determining the structure of monolayers. It has been utilized to verify that subsurface strain occurs in Ge(001)-(2×1) reconstruction.

The bonding of H to the (111) surfaces of Ni, Pd, and Pt has been studied with use of angle-resolved photoelectron spectroscopy. H adsorbed onto a cooled substrate produces photoemission spectra characteristic of chemisorption. In this state the H atoms form an ordered overlayer. Heating the chemisorbed layer to ∼ 300 K results in an irreversible transition of the H atoms into a subsurface site.

In the light of recent neutron-diffraction studies we have reconsidered the critical behavior of Nd. We argue that it is "nearly" second order with $n=2\mathrm{}$ component Heisenberg-model exponents. We also explain, by considering a secondary magnetic order parameter, different temperature dependences for the magnetic satellites around (0,0,3) and (1,0,0). The theoretical prediction of the corresponding exponents $\beta \sim 0.36$ and ${\beta }^{\prime }\sim 1.08$ is in agreement with the experimental values $\beta =0.36\mathrm{}\pm 0.02$ and ${\beta }^{\prime }=1\mathrm{}\pm 0.3$.

We discuss the origin of incommensurate structural modulations as found in certain insulating crystals. The theory developed is based on the necessary existence of a second, independent, transformation mode which can have an energy-lowering interaction with the main mode of transformation only at nonzero wave vector, due to symmetry. The required subsidiary mode, of correct symmetry, has been directly observed, or strongly inferred, in four cases.

Careful studies of intersubband transition energies versus surface electron density have been made in Si(100) inversion layers. An observed change in slope and shift to higher energies at low densities is consistent with a recent model of a two-valley to one-valley occupancy transition driven by many-body effects.

Resonant photoemission measurements have been made to determine the position and width of the Ce $4f^1$ state in CeBi, Ce${\mathrm{Al}}_2$, Ce${\mathrm{In}}_3$, and Ce${\mathrm{Pd}}_3$. As previously found for $\gamma$-Ce both the binding energies and widths in the integral-valence materials are much larger than commonly expected, but are consistent with the virtual-bound-state, local-moment, Kondo-type spin-fluctuation mode. For mixed-valence Ce${\mathrm{Pd}}_3$ the $4f$ emission impinges on the Fermi level.

Photoelectron-spectroscopy studies of Ce${\mathrm{Al}}_2$, La${\mathrm{Al}}_2$, and the "chemically compressed" alloys ${\mathrm{Ce}}_{0.6}$${\mathrm{Y}}_{0.4}$${\mathrm{Al}}_2$ and ${\mathrm{Ce}}_{0.6}$${\mathrm{Sc}}_{0.4}$${\mathrm{Al}}_2$ were performed with use of synchrotron radiation. For all compounds the $4f$ binding energy is 2.55 ± 0.1 eV. These results, combined with previous bulk-property results, motivate a reevaluation of Anderson-model parameters and mechanisms as applied to Ce${\mathrm{Al}}_2$.

Scalar pressure equilibria in which the divergence of the parallel current density vanishes are shown to be free of neoclassical transport (omnigenous), for any asymmetry, any plasma $\beta$, and in any collisionality regime. The explicit constraint that eliminates neoclassical effects in a long, thin mirror equilibrium in the low-$\beta$ limit is derived, and some model fields considered.

We describe a rigorous argument establishing the Berezinski-Kosterlitz-Thouless transition in a class of two-dimensional models including the plane rotator and the Coulomb gas. The main idea is to rewrite correlations in the Coulomb gas as super-positions of correlations in gases of neutral molecules of variable size and small effective activity.

Second-harmonic generation is shown to be sensitive enough to detect molecular monolayers adsorbed on a silver surface. Adsorption of AgCl and pyridine on silver during and after an electrolytic cycle can be easily observed.

A method is proposed which allows a direct determination of the inelastic collision rate of quasiparticles at the gap edge. This method can be explained as follows. Let a supercurrent remove the singularity in the density of states by pair breaking. Since the number of quasiparticles remains constant, they subsequently build up a nonequilibrium population which is extremely well localized near the gap edge. The decay of this excess population can then be observed in the fluctuations of the supercurrent.

Hydrogen evolution and infrared vibrational absorption have been interpreted to show (1) the existence of weakly bonded H in $a$-Ge: H and Ge-rich $a$-Si-Ge: H alloys, and (2) a preference ratio in excess of 5 for the attachment of H to Si over Ge in the formation of such alloys. It is suggested that this may account for the inferior photoresponse of hydrogenated binaries compared to elements, and also for the superiority of $a$-Si: H over $a$-Ge: H. Some ideas on better compensators than H are advanced.

Transient four-wave mixing techniques have been used to measure the decay rate of the excited-state population grating in ${\mathrm{Nd}}_x{\mathrm{La}}_{1-x}{\mathrm{P}}_5{\mathrm{O}}_{14}$ samples as a function of grating spacing. The results show that at room temperature there is diffusive energy migration over distances of the order of 0.36 μm in the highly concentrated samples.

Observed 7-eV satellites in the x-ray—photoemission spectra of U${\mathrm{Ga}}_2$ and other $B$-group compounds are shown to be due to two-hole final states as confirmed by existing Auger data. The presence of these satellites is an indication for a weak $\mathrm{fd}$ hybridization and, when compared to uranium—transition-metal compounds, increased $5f$ localization.

Significant field effects have been reported in chalcogenide glasses, despite the pinning of the Fermi energy by valence alternation pairs. It is shown that the existence of a potential barrier between the two neutral defect centers is responsible for this, but the field effect should decay away with time. It is predicted that the relaxation times are temperature activated, and the activation energies can be used to determine the density of localized states in the gap. New experimental data are reported which demonstrate all of these effects.

Using inequalities, we give a simple proof that the surface tension $\tau$ of an Ising model with interaction $\beta J=K$ on a $d$-dimensional lattice, ${\sigma }_i=\pm 1$, satisfies the inequality $\frac{d_{\tau }\mathrm{}\left(K\right)\mathrm{}}{\mathrm{dK}}>~2{\left[m^{*}\mathrm{}\right(K\left)\right]}^2$, where $m^{*}\mathrm{}\left(K\right)\mathrm{}$ is the spontaneous magnetization. When combined with our previous results that $\tau =0\mathrm{}$ for temperatures above $T_{c,s}$, the critical temperature for spontaneous magnetization, this proves that (i) $\tau =0\mathrm{}$, for $T>\mathrm{}{T}_c$, and $\tau >0\mathrm{}$, for $T<\mathrm{}{T}_c$, the critical temperature for the full $d$-dimensional system; and (ii) $T_{c,s}=T_c$. (Both results were known only for $d=2\mathrm{}$).