Instantaneous diffusion effect on spin-echo decay: Experimental investigation by spectral selective excitation - art. no. 174423

The influence of the instantaneous diffusion process on spin-echo decay of E-gamma' centers in gamma irradiated silica is experimentally probed by spe ctral selective excitation within their inhomogeneous resonance line. Our r esults evidence the different effectiveness of this dephasing mechanism on varying the resonance field, manifesting itself by a faster decay of the ec ho signal when generated by spin packets located in the central part of the spectrum. It is shown that the dependence of the instantaneous diffusion r ate on the spectral position of echo-active spins reproduces the shape of t he E-gamma' centers resonance spectrum. These features are discussed in the framework of theoretical models concerning the transversal spin relaxation in solid systems and point out the correlation between the instantaneous d iffusion rate and the concentration of echo-active spins located within a s pectral bandwidth of the order of the Rabi frequency.