Asymmetry parameter orientation-averaged

The nature of the orientational disorder in phases III and II was investigated first by powder experiments to give an overview of the evolution of the anisotropy and asymmetry parameter of the averaged EFG interaction. In all phases, the EFG asymmetry parameter is different from zero, and continuously decreases as temperature increases, with no observed anomaly at the transition temperature. That the asymmetry is definitively nonzero over the whole temperature range shows that the planar reorientational motion consists of jumps over six asymmetric potentials wells, which retain the centrosymmetry on average, and that the population of the different sites continuously evolves with temperature. The authors argued that a precise estimation of the two unknown occupation probabilities cannot be drawn from powder spectra without simplifying assumptions. The reasons come from the model of sixfold jump around the axis normal to the benzene... 

Mungal and coworkers [9,33,81] conducted simultaneous measurements of velocity and OH/CH fields in deflected jet flames. The burner was oriented at 0°, 45° and -45° to the crossflow. Measured parameters include the contours of the OH/CH layer, mean velocity profiles and shear strain rate. Figure 29.18 shows the average velocity profile along the direction of crossflow at various axial locations in the flame [9]. The profiles clearly show the asymmetry caused by the crossflow stream. The authors also observed a lower mean strain rate on the lee side of the burner. 

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