Comment on: “Photoionization of helium-like ions in asymptotic non-relativistic region” [Phys. Lett. A 358 (2006) 211]

The results of Mikhailov et al. [A.I. Mikhailov, A.V. Nefiodov, G. Plunien, Phys. Lett. A 358 (2006) 211] on single and double ionization of He at high energy can be obtained quite simply by combining two previous results long well known in the literature. The results of Mikhailov et al. can also be understood in a larger context, using an asymptotic Fourier transform approach, which also allows a justification of various statements assumed but not demonstrated by Mikhailov et al.     

Water adsorption and dissociation on BeO(0 0 1) and (1 0 0) surfaces

Plateaus in water adsorption isotherms on hydroxylated BeO surfaces suggest significant differences between the hydroxylated (1 0 0) and (0 0 1) surface structures and reactivities. Density functional theory structures and energies clarify these differences. Using relaxed surface energies, a Wulff construction yields a prism crystal shape exposing long (1 0 0) sides and much smaller (0 0 1) faces. This is consistent with the BeO prisms observed when beryllium metal is oxidized. A water oxygen atom binds to a single surface beryllium ion in the preferred adsorption geometry on either surface. The water oxygen/beryllium bonding is stronger on the surface with greater beryllium atom exposure, namely the less-stable (0 0 1) surface. Water/beryllium coordination facilitates water dissociation. On the (0 0 1) surface, the dissociation products are a hydroxide bridging two beryllium ions and a metal-coordinated hydride with some surface charge depletion. On the (1 0 0) surface, water dissociates into a hydroxide ligating a Be atom and a proton coordinated to a surface oxygen but the lowest energy water state on the (1 0 0) surface is the undissociated metal-coordinated water. The (1 0 0) fully hydroxylated surface structure has a hydrogen bonding network which facilitates rapid proton shuffling within the network. The corresponding (0 0 1) hydroxylated surface is fairly open and lacks internal hydrogen bonding. This supports previous experimental interpretations of the step in water adsorption isotherms. Further, when the (1 0 0) surface is heated to 1000 K, hydroxides and protons associate and water desorbs. The more open (0 0 1) hydroxylated surface is stable at 1000 K. This is consistent with the experimental disappearance of the isotherm step when heating to 973 K.     

Clocking hadronization in relativistic heavy-Ion collisions with balance functions

A novel state of matter has been hypothesized to exist during the early stage of relativistic heavy-ion collisions, with normal hadrons not appearing until several fm/c after the start of the reaction. To test this hypothesis, correlations between charges and their associated anticharges are evaluated with the use of balance functions. It is shown that late-stage hadronization is characterized by tightly correlated charge-anticharge pairs when measured as a function of relative rapidity.     

Dyes as quenchers of singlet oxygen

The magnitude of solvent isotope effects on the rate of the dye sensitised photo-oxidation of alkenes is dependent upon the nature and concentration of the dye. An explanation, involving quenching of singlet oxygen by the dye, is proposed.     

The thermodynamic properties of solid cobalt—zinc alloys

Reversible potentials of galvanic cells of the form: Pt/(CoZn)(alloy)+ZnO/ZrO₂+CaO/O₂(air)/Pt have been measured at temperatures in the range 873–1173 K. The results have been used to derive the thermodynamic activities and the partial and integral free energies, enthalpies and entropies of formation of the α(f.c.c.) solid solutions and of the β₁, γ, γ₁, γ₂ and δ intermediate phases. Exothermic heats of formation and negative entropies of formation are observed throughout the system. The enthalpies of formation of the f.c.c. solid solutions are compared with those of similar cobalt-based examples and the apparent influence of electronic factors is discussed. An analysis is attempted of the factors contributing to the entropies of formation of the solid phases and their Debye temperatures are estimated.     

Limitations on the validity of the non-relativistic dipole approximation for photoelectron angular distributions

We present results which exhibit hazards in the use of the non-relativistic dipole approximation in the interpretation of experimental photoelectron angular distributions. Significant deviations from the non-relativistic dipole approximation occur for both low and high Z atoms. In light elements these effects are found in the keV range and even below. In heavy elements they are found even for energies very close to threshold. For total cross sections, in contrast to this angular distribution situation, the surviving integrated relativistic and multipole corrections tend to cancel, so that the non-relativistic dipole approximation holds to surprisingly high energies.     

The relation of percolation to energy migration dynamics

Numerical solutions are presented of a master equation for energy migration among conducting sites on a lattice, averaged over site configurations for a given concentration. The relation between static percolation phenomenon and the dynamics of energy migration is explored.