Coupled (localized+delocalized) electron spins dynamics in polymer phase of RbC60 fulleride

The transverse response (transverse dynamic susceptibility) of coupled localized (s) and delocalized (e) electron spins of a metal paramagnet as well as the longitudinal dynamic response of such a system (to be registered by a longitudinal coil) to the modulation of microwave power saturating electron spin resonance (ESR) are calculated. The ESR spectrum is analytically decomposed into two Lorentzians with normal resonance frequencies and decay rates of the coupled localized +delocalized electron spin system. In the case of relaxationally coupled s- and e-spins the longitudinal response is decomposed into two “relaxational” Lorentzians squared with amplitudes containing ESR lineshapes with above-mentioned shifted frequencies and linewidths as well as enhancement-suppression coefficients of magnetization evolution. These results are essential for the interpretation of experiments on longitudinal response in metal paramagnets, the latter being the source of important information on longitudinal electron relaxation; in particular, for extraction of information from longitudinal response experiments in the polymer phase of RbC₆₀ fullende, where the obtained results describe the observed form of the ESR spectrum and the main features of the longitudinal response.