ENDOR spectroscopy: a tool for the study of radical structures and motions in the solid state.

We show that the analysis of ENDOR lineshapes and enhancements can give valuable information on the dynamics of radicals in the solid state. The basic advantage of ENDOR with respect to EPR spectroscopy resides in its greater spectral resolution, which positively affects also its potentiality in studying molecular motions in solids. In fact, we show that the dynamical effects on the lineshapes are detectable by using ENDOR spectroscopy in a larger range of correlation times. The range can be still more wide if the radical dynamics gives rise to an efficient relaxation mechanism which influences the spin populations. In this case, the motions can be studied through the analysis of the ENDOR enhancements, which in some cases became a very sensitive probe