Molecular dynamics study of orientational order and rotational melting in clusters of TeF 6

Molecular dynamics simulations of the behavior of molecules in crystalline clusters of TeF 6 were carried out on systems of 100, 150, 250, and 350 molecules. Several diagnostic functions were applied to investigate whether rotational melting occurred before translational melting. These functions included the coefficient of rotational diffusion D θ ( T ), the “orientational Lindemann index” δ θ ( T ), the “orientational angular distribution function” Q (θ, T ), and the “orientational pair-correlation function” g θ ( r, T ). All indicators implied that rotational melting occurred before translational melting, that it began with the outermost molecules, and that its onset for smaller clusters was at lower temperatures than for larger clusters. Results also showed that the rotational transition coincided with the transition from a lower symmetry phase (monoclinic) to cubic, a phenomenon that had been noted by others to occur with some regularity for systems of globular molecules.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43961/1/10053_2005_Article_BF01426586.pd

Quantitative one-dimensional single-pulse multi-species concentration and temperature measurement in the lift-off region of a turbulent H2/air diffusion flame

Brockhinke A, Andresen P, Kohse-Höinghaus K. Quantitative one-dimensional single-pulse multi-species concentration and temperature measurement in the lift-off region of a turbulent H2/air diffusion flame. APPLIED PHYSICS B. 1995;61(6):533-545.In this article, we report on one-dimensional single-pulse measurements of temperature and major-species concentration (O-2, N-2, H2O and H-2) in a turbulent H-2/air jet diffusion flame using Raman and Rayleigh scattering of KrF* excimer-laser radiation. Spatial resolution of approximate to 0.5 mm along a 6 mm long line has been obtained, with reasonable error limits for mole fraction (Delta chi = 5% for N-2 detection) and temperature (Delta T = 8%) determination at flame temperatures. We present various profiles showing the composition and temperature along a line at different heights in the flame with particular emphasis on the lift-off region (i.e. low x/D). In this zone, temperature and mixture fraction can be determined simultaneously - from a single laser pulse - in a spatial region extending from unburnt gas in the center of the jet across the flame front into the cool air of the surrounding atmosphere. This allows for the first time the systematic study of the shape and width of the high-temperature region and the corresponding concentration and temperature gradients. The comparison of averaged data and scatter plots with previous pointwise measurements shows good agreement