Viscosity Regime Research Articles

Seismic reflection and refraction studies for investigating fault zones along the Geotraverse Rhenoherzynikum

In 1973 detailed seismic crustal studies were performed across the prominent fault zone between the Hercynian fold systems of the Rhenish Slate Mountains (western part of Rhenoherzynikum) and the Saar-Nahe trough. Reflection data show a zone of strongly dipping reflectors, separated from another area with nearly horizontal layering. Data from refraction stations confirm the picture of a fault zone cutting two old crustal blocks down to the Moho. A similar but smaller survey was performed in 1975 across the western Rhine graben fault near Landau. This fault is tensionsal and could not be observed with the same certainty and up to the same depth range as the former one. Apparently, its dip near the surface is smaller than anticipated and may even assume still smaller values at intermediate crustal depths. Moreover, high temperatures in this area tend to limit the maximum depth of the fault zone, in accordance with the concept of a direct relationship between the depths of seismicity along faults and the temperature—viscosity regime. The area between the two reflection surveys was studied by refraction observations, making use of the shots of the reflection work. In general, the reflection investigations are well able to reveal the geometry and the maximum depth of fault zones and show many structural details, while the supplementing refraction work determines the overall velocity depth relation and may follow important horizons.

ESR lineshapes in viscous liquids. 1. Relaxation Due to secular interactions: “Principal line” analysis

Line shapes have been calculated for the ESR spectra of slow-tumbling molecules with anisotropic g-factors and no hyperfine interactions, and measurements have been made for such a molecule, (n-C 4H 9) 4NNiS 4C 4(CN) 4, over a wide range of viscosities. Axially symmetric g-tensors and isotropic rotational diffusion have been assumed and, at high viscosity, only secular terms have been included. The agreement between experiment and theory is encouraging, but discrepancies occur because the temperature dependence of the components of the g-tensor have been neglected. The “principal” portion of the spectrum can be well-described by means of a Lorentzian line plus a dispersive contribution with the same width and at the same frequency. By simply studying this “principal” line, one can obtain good information concerning the rotational correlation time for slow-tumbling molecules. At moderate viscosities, the lines are slightly asymmetric, exhibit a secular shift, and are much narrower than predicted by perturbation theories valid in the extreme motionally narrowed (low viscosity) regime. In properly reduced units, the linewidths, secular shifts, and spectral asymmetries for molecules with axially symmetric g-tensors can all be represented by functions which are independent of the particular values of the g-tensor. The theory can readily be extended to secular hyperfine interactions. The principal line becomes the “perpendicular line” in the solid, and an extension of the theory allows one to study the “parallel line” as well.

Decay of the triplet state I. First-order processes in solution

The decay of the trip let states of naphthalene, 2-bromonaphthalene, anthracene, 1,5-dichloroanthracene and 9-bromophenanthrene have been studied in isopentane solution over the temperature range 22 to —196 °C and in propylene glycol solution from 54 to —80 °C, corresponding to a variation in viscosity by a factor of 10 8 . An experimental arrangement for flash photolysis investigations at low temperatures is described. When allowance is made for discontinuities in the viscosity-temperature relations all our measurements are accounted for in terms of two regimes of trip let decay: a high viscosity regime where rate is nearly independent of temperature and viscosity and the mechanism is truly unimolecular and a low viscosity regime w here diffusion-controlled quenching processes are operative.