Recent experimental results have stimulated this investigation of the potential of interaction, $V\left(\overrightarrow{\mathrm{r}}\right)$, between a He atom and the (111) surface of diamond. The potential has been computed with various assumptions concerning the presence and configuration of hydrogen adatoms on the surface. Good agreement with He scattering measurements is obtained in the case of a (1×1) overlayer with each carbon atom terminated by a single hydrogen adatom of which the C-H bond Length is 1.09 Å.

The stability of successive layer formation relative to bulk cluster growth of molecules adsorbed on graphite has been studied by reflection high-energy electron diffraction. It is found that at low temperature clustering occurs in ${\mathrm{N}}_2$ and Ne on top of two molecular layers, whereas multilayer formation continues to at least ten layers in Xe and Ar. These results contradict the predictions of recent atomistic theories of film stability.

Combined magnetotransport and cyclotron-resonance experiments in a two-dimensional hole system at a modulation-doped GaAs-(AlGa)As heterojunction show that the Kramers degeneracy of the lowest subband is lifted for finite $k$ giving rise to two cyclotron masses ${m_1}^{*}=0.38\mathrm{}{m}_0$ and ${m_2}^{*}=0.60\mathrm{}{m}_0$ at $E_{\mathrm{F}}=2.4\mathrm{}$ meV. The observation of plateaus in ${\rho }_{xy}$ shows that the quantized Hall effect is independent of the details of the host band structure.

Photoconductivity measurements on $\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}-{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ heterostructures with photon energies $0.05 \mathrm{meV}<h\nu <0.14\mathrm{} \mathrm{meV}$ show resonance structures with a half-width of less than 0.002 meV in the magnetic field range $3 \mathrm{T}<B<\mathrm{}8\mathrm{} \mathrm{T}$. The resonances are only observed at magnetic field values where the Fermi level is located between spin-split levels and are attributed to electron spin resonance. The $g$ factor depends on the carrier density. The linear extrapolation of the resonance energy to $B=0\mathrm{} \mathrm{T}$ leads to a finite excitation energy.

Far-infrared magnetotransmission experiments on $n$-type InSb in the parallel Voigt geometry ($\overrightarrow{\mathrm{E}}\parallel \overrightarrow{\mathrm{B}}\perp \overrightarrow{\mathrm{k}}$) conclusively demonstrate that the electric-dipole-excited spin resonance (EDSR) of conduction and donor-bound electrons in this material is allowed through lack of inversion symmetry. Quite unexpectedly for this geometry, the EDSR spectra also reveal an anomalous dependence on the sign of either $\overrightarrow{\mathrm{B}}$ or $\overrightarrow{\mathrm{k}}$. It is shown, through time-reversal-symmetry arguments, that the above behavior represents an explicit contribution of the photon momentum to the dielectric response function.

The order-of-magnitude discrepancy between the predictions of the weak-coupling theory of charge-density-wave transitions and the observations is rectified by construction of a microscopic strong-coupling theory. The essential ingredients of the theory are the strong wave-vector dependence of electronically induced anharmonicity and mode-mode coupling which are shown to strongly depress the transition.

It has been found that some charged, rotating black holes are unstable to the growth of a small, perturbing, massless scalar field. Additionally, there are strong indications that some uncharged black holes will be unstable to gravitational and electromagnetic perturbations as well.

A modified form of percolation theory is solved exactly on a Cayley tree of arbitrary coordination number. In this model, cluster growth proceeds "dynamically" by invasion along a path of least resistance. Although there are clear parallels to ordinary "static" percolation at the percolation threshold, there are also significant differences. In particular, the scaling function which describes the shape of large clusters is different in the two models.

Phase-locked solitary waves are shown to be the stable fixed points of an infinite-dimensional map obtained from a bistable optical ring cavity.

Particles diffusing in $d$-dimensional space among a random distribution of stationary spherical traps are considered. Given a particle at the origin at time $t=0\mathrm{}$, it is shown that the density of particles at the origin as $t\to \infty$ must decay at least as fast as $\exp [-t^{\frac{d}{\mathrm{}(d+2\mathrm{})\mathrm{}}}]$. The density here is obtained by averaging the diffusive field for a given configuration of traps over all configurations. The present upper bound coincides with the lower bound recently derived by Grassberger and Procaccia.

The asymptotic large-momentum-transfer behavior of the deuteron form factor and the form of the deuteron distribution amplitude at short distances are derived from perturbative quantum chromodynamics. The fact that the six-quark state is 80% hidden color at small transverse separation implies that the deuteron form factors cannot be described at large $Q^2$ by meson-nucleon degrees of freedom, and that the nucleon-nucleon potential is repulsive at short distances.

By adding the trivial term $-d{t}^2$ one can convert the four-dimensional (positive-definite) Newman-Unti-Tamburino line element into a static solution of the five-dimensional vacuum Einstein equations. Interpreted $\stackrel{`}{a}\mathrm{la}$ Kaluza and Klein, the solution describes a monopole with a charge-to-mass ratio of $\sqrt{2}$ in rationalized Planck units. Although it is a perfectly regular five-geometry it appears singular from a four-dimensional perspective.

The existence of the $\gamma$ branch in the decay of the ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ shape isomer is confirmed by the observation of an $E0$ transition between the isomer and the ground state. The data are consistent with the excitation energy of 2558 keV, spin of $0^{+}$, and half-life of ≈ 200 ns of the isomer.

A multistep $\alpha$-particle-transfer picture is used to describe anomalous back-angle elastic scattering of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$+${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. Transfer of two and three $\alpha$ particles is described in a semiclassical treatment of the interplay between absorption and transfer processes. The energy dependence of the anomalous contribution to the elastic $S$ matrix due to these processes is estimated and shown to be consistent with the overall trend of the data.

Detailed studies have been made of the multiplicity, energy, and angular distributions of $\alpha$ particles emitted in coincidence with fission fragments from the ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ + ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ ($E_{\mathrm{lab}}=465\mathrm{}$ MeV) reaction. Approximately 90% of the $\alpha$ particles are evaporated from the two fully accelerated fission fragments. The remaining $\alpha$ particles have a strongly enhanced emission probability in the direction perpendicular to the scission axis, suggesting the contact or neck region between the fragments as the source of these particles.

Neutron stars for which the ratio $\frac{T}{\mathrm{}\left|W\right|\mathrm{}}$ of kinetic to gravitational potential energy exceeds ∼ 0.08 are likely to be unstable and to spin down by gravitational-wave—driven oscillations. A class of pulsars with nearly identical frequencies may thus result from the collapse of accreting, rapidly rotating white dwarfs. It is likely that the fast pulsar, PSR 1937 + 214, rotates more slowly than this, but the question remains open partly because of uncertainty in the equation of state.

New effects in heat-conducting nonequilibrium fluids near critical points are predicted theoretically: The heat conductivity gains a new divergent contribution and the heat diffusivity becomes strongly nonisotropic.

A systematic weak-coupling expansion is developed for the Liouville quantum field theory on a periodic spatial interval. Matrix elements of various Liouville operators are computed to order $g^8$ by perturbation in nonzero modes about the exact solution of the zero-mode problem. To this order the results agree with the explicit operator solution given previously by Braaten, Curtright, and Thorn, in which the Liouville field was expressed in terms of a free pseudoscalar field by means of an operator Bäcklund transformation.

The relationship between heavy- and light-quark systems is examined. By use of a Bogoliubov-Valatin transformation the author shows how to interpolate continuously between heavy-quark atomic models and light-quark collective models of the hadrons.