Volume 115, Issue 7, 15 August 2001
Index of content:
The solid–liquid interfacial free energy of close-packed metals: Hard-spheres and the Turnbull coefficient115(2001); http://dx.doi.org/10.1063/1.1391481View Description Hide Description
Largely due to its role in nucleation and crystal-growth, the free energy of the crystal-melt interfacial free energy is an object of considerable interest across a number of scientific disciplines, especially in the materials-, colloid-, and atmospheric sciences. Over 50 years ago, Turnbull observed that the interfacial free energies (scaled by the mean interfacial area per particle) of a variety of metallic elements exhibit a linear correlation with the enthalpy of fusion. This correlation provides an important empirical “rule-of-thumb” for estimating interfacial free energies, but lacks a compelling physical explanation. In this work we show that the interfacial free energies for close-packed metals are linearly correlated with the melting temperature and are therefore primarily entropic in origin. We also show that the slope of this linear relationship can be determined with quantitative accuracy using a hard-sphere model, and that the correlation with the enthalpy of fusion reported by Turnbull follows as a consequence of the fact that the entropy of fusion for close-packed metals is relatively constant.
Photodetachment of Observation of charge-transfer states and the transition state of hydrogen abstraction reaction115(2001); http://dx.doi.org/10.1063/1.1394758View Description Hide Description
We report a photoelectron spectroscopic study of at 193 and 157 nm. In addition to a detachment feature from we observed a higher binding energy feature in all spectra due to ionization of the solvent molecules leading to charge-transfer states. Detachment of an electron from in reaches the transition state region of the reaction, The bound to non-bound transition resulted in a long tail at the low binding energy side in the photoelectron spectrum of We estimated that the neutral complex at the anion geometry, which is near the transition state region of the H-abstraction reaction, is 6±1 kcal/mol above the asymptote, consistent with a previous estimation of a 4 kcal/mol entrance barrier height for this reaction.
115(2001); http://dx.doi.org/10.1063/1.1395056View Description Hide Description
Computer simulations of bubble oscillations revealed that the bubble temperature at the collapse is highest for a moderately low acoustic amplitude because at higher acoustic amplitudes the bubble content is mostly vapor. The light emission of multibubble sonoluminescence is a combination of chemiluminescence and plasma emissions.
Fluoroalcohols as nucleating agents in supersaturated vapors: Efficient clustering with water in the vapor phase115(2001); http://dx.doi.org/10.1063/1.1394937View Description Hide Description
Fluoroalcohols in small concentrations in the vapor phase display striking enhancing effects on homogeneous nucleation of supersaturated aliphatic alcohols, and on the formation of water clusters by supersonic expansion. The enhanced nucleationeffects are attributed to the surfactant properties of fluoroalcohols, which lower the surface tension of the growing droplets, and therefore lower the barrier to nucleation.