Fractons relaxation

Pescia J, Misra SK, Zaripov M. 1999a. Evidence for spin-fracton relaxation in the polymer resin P4VP doped with Co ", Nd ", Yb ". P/zys Rev Lett 83 1866-1869. 

Relaxation rate, which looks into the low-frequency vibrational modes of protein molecules, is considered to play a significant role in biological process. A fractal-related parameter, called the fracton dimension, d-p, has been used to describe the relaxation rate at low temperature.f ... 

We measured the temperature-dependance of the spin-lattice relaxation time, for various alumino-silicate aerogels, corresponding porous glasses and crystalline counterparts. The purpose of these experiments is threefold (i) to compare the relaxation response of these very porous amorphous materials to the general one of more classical glasses, (ii) to see whether fractons, whose vibrationnal amplitudes are large, contribute to relaxation mechanisms, (iii) to follow - through variations of the density - the dependance of this dynamical property on the structural parameters, (iv) to test the theoretical predictions about relaxation in disordered systems proposed by R. Orbach and S. Alexander. 

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