Relaxation phenomena show up in standard energy domain Mossbauer spect
ra via line broadening. The evaluation of such spectra is in most case
s done by adopting the stochastic theory mainly developed in the 60s a
nd 70s. Due to the time structure and the polarization of the synchrot
ron radiation nuclear resonance forward scattering in the time domain
gives valuable information on relaxation mechanisms. We report here ma
inly on Nuclear Forward Scattering (NFS) experiments investigating the
paramagnetic relaxation of the Fe3+ ion in (NH)(4)(Al0.95Fe0.05)-Fe-5
7(SO4)(2) . 12H(2)O and briefly on recent investigations on charge flu
ctuations in Eu3S4.