The connectivity properties of liquid water are studied with molecular dynamics. It is found that the hydrogen-bonded network includes tiny spatially correlated "patches" of four-bonded molecules, and that the local density near a "patch" is lower than the global density. The diameter of the finite patches increases with decreasing temperature, and is comparable to the characteristic length scale of density fluctuations recently measured by small-angle x-ray scattering.

Cross sections for the reaction ${}_{}{}^3{}_{}{}^{}\mathrm{He}(K^{-}, K^{+}n)H$ are estimated. This process affords a promising way of producing the stable six-quark dibaryon $H$ ($0^{+}$, $I=0\mathrm{}$, strangeness - 2) predicted by the bag model.

The discovery of a monopole with Dirac magnetic charge, $\frac{e}{2\alpha }$, would imply absolute quark confinement and forbid any free, fractional electrically charged particles, if no unknown long-range forces exist. Further, unification of electromagnetism and QCD would be required. The monopole also carries screened color magnetic fields. Certain alternatives to QCD in which the SU(3) gauge symmetry is broken, partially or completely, are excluded. The inflationary-universe scenario based on SU(5) grand unified theory would be excluded.

Evidence is presented for the occurrence of a ${\frac{5}{2}}^{\pm }$ parity doublet as the ground state of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Pa}$, in agreement with a previous theoretical prediction. The doublet splitting energy is measured to be 0.22±0.05 keV. The relation of this doublet to ground-state octupole deformation is discussed.

The Lamb shift in hydrogenic phosphorus ($Z=15\mathrm{}$) has been measured by the $2s_{\frac{1}{2}}-2\mathrm{}{p}_{\frac{3}{2}}$ laser resonance-quenching method. An efficient synchronization between the light pulse from a tunable dye laser, pumped by a nitrogen laser, and the beam bursts of a cyclotron is used to enhance up to 0.8 the signal-to-background ratio. From the measured $2s_{\frac{1}{2}}-2\mathrm{}{p}_{\frac{3}{2}}$ energy splitting, $\lambda =5556.5\mathrm{}\left(2.5\right)\mathrm{}$ Å, and the calculated fine-structure splitting the Lamb shift $S=20.18\mathrm{}\left(25\right)\mathrm{}$ THz was deduced. This result is confronted with the presently available calculations of QED.

A self-consistent, parameter-free approach is described which allows one to calculate the lattice distortion around neutral and charged simple defects. The method is applied to the Ga-site single donor Ge in Gap. It is predicted that the nearest-neighbor atoms of the impurity move towards the impurity. The influence of an ionization of the defect on this lattice relaxation is found to be very small. The results are interpreted in terms of simple mechanisms.

The local-density approximation and the linear muffin-tin orbital method have been used within the atomic-sphere approximation to calculate structural energy differences for all the alkaline earth metals at zero temperature. At ordinary pressure the calculations predict the crystal structure sequence hcp→fcc→bcc as a function of atomic number. As a function of pressure they predict the structure sequence fcc→bcc→hcp. The structural transitions and the onset of superconductivity under pressure are correlated with the $d$ occupation number.

The crystal structure of the high-pressure phase of cesium (IV) was determined to be a tetragonal lattice with $Z=4\mathrm{}$. The space group is ${D_{4h}}^{19}-\frac{I{4}_1}{\mathrm{amd}}$ and the lattice parameters are $a=3.349\mathrm{}$ Å and $c=12.487\mathrm{}$ Å at 8.0 GPa. From the structure it is deduced that the atomic radius of cesium decreases dramatically at the III-IV transition, which suggests a discontinuous $s-d$ electronic transition.

The effect of pressure on the optical properties of Rb and Cs is studied by reflection spectroscopy. Under pressure, both metals exhibit a strong increase of the interband absorption with prominent structure below 3 eV. The strength of the absorption is intimately related to a transfer of conduction electrons from $s$- into $d$-like states. The optical properties provide conclusive evidence that the pressure-induced bcc-fcc transition in both metals occurs at the same critical value of $d$-band occupancy.

A polarized beam of low-energy positrons has been used for the first time as a probe of surface magnetism. The polarization, $P_{e^{-}}$, of electrons captured at a Ni(110) surface to form positronium is measured. The temperature dependence of $P_{e^{-}}$, fitted by a power law, yields an exponent of ${\beta }_1=0.7\mathrm{}\pm 0.1$, in qualitative agreement with calculations of the critical exponent for the surface-layer magnetization. Rapid quenching of the ferromagnetic order is observed for submonolayer coverages of oxygen.

Auger electrons from magnetically ordered solids are spin polarized. As an example ferromagnetic ${\mathrm{Fe}}_{83}$${\mathrm{B}}_{17}$ glass was studied. The polarization of the Fe Auger electrons exhibits structures on the order of 20%, both parallel and opposite to the magnetization of the sample depending on the particular transition. Auger electrons from B are unpolarized. The technique opens new perspectives in the study of magnetic solids, particularly alloys and compounds.

From an Auger study of dilute Ni alloys with electropositive metals it is concluded that multiplet splitting of the Ni $d^8$ configuration is important. It is shown that the $d^8$ (${}_{}{}^3{}_{}{}^{}F$) state is of sufficiently low energy to be strongly mixed in the Ni ground-state wave function whereas the other, mainly singlet, states are all well removed to higher energy. The relevance of multiplet splittings to polarity fluctuations and magnetism in transition metals and their alloys is discussed.

The scattering of a pulsed supersonic beam of vibrationally excited $v^{\prime }=1\mathrm{}$, $J^{\prime }=\frac{3}{2}$ nitric oxide molecules, prepared by tunable ir laser excitation, off LiF and Ca${\mathrm{F}}_2$ surfaces has been investigated by resonantly enhanced two-photon ionization. A survivial probability of less than 2.3×${10}^{-4\mathrm{}}$ has been found. Similarly, an upper limit of less than 2×${10}^{-3\mathrm{}}$ can be given for an energy transfer into other rotational states of $v^{\prime }=1\mathrm{}$ or high $J^{\prime \prime }$ of $v^{\prime \prime }=0\mathrm{}$. The present results will be compared with the predictions of a recent theoretical model calculation.

The sun's internal angular velocity is estimated from observations of rotational splitting of low-order, low-degree global oscillations detected as fluctuations in the limb-darkening function. The inferred rapid rotation implies a unitless grativational quadrupole moment, $J_2$, of (5.5±1.3)×${10}^{-6\mathrm{}}$. When this result is combined with two published planetary radar results, values of 0.987±0.006 and 0.991±0.006 are obtained for $\frac{1}{3}(2+2\mathrm{}\gamma -\beta )$, a quantity equal to 1 in the general theory of relativity.

It is shown that the entropy of the radiation evaporated by an uncharged, nonrotating black hole into vacuum in the course of its lifetime is approximately $\frac{4}{3}$ times the initial entropy of this black hole. Also considered is a thermodynamically reversible process in which an increase of black-hole entropy is equal to the decrease of the entropy of its surroundings. Implications of these results for the generalized second law of thermodynamics and for the interpretation of black-hole entropy are pointed out.

The ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}(\alpha , {\alpha }^{\prime }f)$ cross section was measured at $E_{\alpha }=120\mathrm{}$ MeV for the scattering angle interval 0°-3°. By comparison of the fission-coincident inelastic alpha spectra in the ranges 0°-1.5° and 1.5°-3°, it is possible to deduce the shape of the giant monopole resonance in ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. It was found to be located at $E_x\sim 77A^{-\frac{1}{3}}$ MeV and to have a width $\Gamma$ (full width at half maximum) ∼ 6 MeV. If one assumes a fission probability similar to that of the giant dipole resonance, it exhausts about 80% of the isoscalar $E0\mathrm{}$ energy-weighted sum rule.

The Hohenberg-Kohn theorem is extended to fractional electron number $N$, for an isolated open system described by a statistical mixture. The curve of lowest average energy $E_N$ versus $N$ is found to be a series of straight line segments with slope discontinuities at integral $N$. As $N$ increases through an integer $M$, the chemical potential and the highest occupied Kohn-Sham orbital energy both jump from $E_M-E_{M-1\mathrm{}}$ to $E_{M+1\mathrm{}}-E_M$. The exchange-correlation potential $\frac{\delta E_{\mathrm{xc}}}{\delta n\left(\overrightarrow{\mathrm{r}}\right)}$ jumps by the same constant, and $\frac{{\lim }_{r\to \infty }\delta E_{\mathrm{xc}}}{\delta n\left(\overrightarrow{\mathrm{r}}\right)}>~0$.

The excitation of fluorescently labeled polymer coils by shallow optical evanescent waves permits measurement of the local monomer solute concentration in the vicinity of a nonadsorbing wall over controlled, submicroscopic distances. The existence of a depletion layer at the solid-solution interface is thus demonstrated directly for the first time. The results obtained on a 103 000-molecular-weight polystyrene sample dissolved in ethyl acetate are in agreement with the entropic repulsion model.

It is shown that the laser intensity modifies the configuration mixing of the ground state, intermediate states, and autoionizing states in multiphoton ionization and autoionization. To illustrate the intensity effect on autoionization, a calculation is presented for three-photon ionization of the Sr atom near the $\mathrm{}\left(5p6s\right)\mathrm{}{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ autoionizing resonance in a range of laser intensities employed in recent experiments.

In a series of experiments using two-, four-, and eight-beam 10.6-μm-laser irradiation of a variety of target geometries, a significant amount of energy was found to be deposited in regions remote from the focal spots. The deposition patterns can be predicted with a self-generated magnetic field model.