arXiv subjects

R. Stephen Berry

Publications and source records attributed to R. Stephen Berry.

3 recordsLinked to original sources

arXiv2003

How Hot Is Radiation?

A self-consistent approach to nonequilibrium radiation temperature is introduced using the distribution of the energy over states. We begin rigorously with ensembles of Hilbert spaces and end with practical examples based mainly on the far from equilibrium radiation of lasers. We show that very high, but not infinite, laser radiation temperatures depend on intensity and frequency. Heuristic "temperatures" derived from a misapplication of equilibrium arguments are shown to be incorrect. More general conditions for the validity of nonequilibrium temperatures are also established.

cond-mat.stat-mech↗

arXiv2001

On the proximity relation between two surface-melted clusters involved in inter-cluster mass-transfer

We explore the way free particles produced by dissociating ``particle-hole pairs'' on a surface-melted cluster can be transferred to a second, nearby surface-melted cluster. This mass transport is based on an inter-cluster direct transfer mechanism of the particles. We found that in this particular case one cluster may grow at the expense of another, obeying a temporal power law with the exponent 1/2 for the average radius R = const t^{1/2}. The change from the expected universal power law R = const t^{1/3} is a consequence of the proximity relation between these two clusters which lead to enhance the effective transport rates.

physics.chem-ph↗

arXiv1999

Symmetry in Order-Disorder Changes of Molecular Clusters

The dynamic orientational order-disorder transition of clusters consisting of octahedral molecules is formulated in terms of symmetry-adapted rotator functions. The transition from a higher-temperature body-centered-cubic, orientationally disordered phase to a lower-temperature, monoclinic, orientationally-ordered phase is a two-step process. The higher-temperature transition has two local minima in the free energy, like a finite-system counterpart of a first-order transition. Simulations show the lower-temperature transition is continuous. The analytic theory predicts a temperature of 27K for this transition, for a 59-molecule cluster of tellurium hexafluoride in a good agreement with the ~30K result of canonical Monte Carlo calculations.

physics.atm-clus↗