Paramagnetic relaxation as seen by nuclear resonant forward scattering of synchrotron radiation

Nuclear forward scattering of synchrotron radiation, which can be regarded as Mossbauer spectroscopy in the time domain, is a very promising tool for the investigation of dynamic phenomena. The interpretation of the resulting time-dependent intensity of the scattered radiation can be achieved by inc orporating the stochastic theory of line shape into the program package SYN FOS, the theoretical basis of which has been described in an earlier paper [Haas et nl., Phys. Rev. B 56, 14 082 (1997)]. This is demonstrated by mean s of measurements carried out on the paramagnetic iron porphyrin complex [F e(CH3COO)(TPpivP)](-) that exhibits dynamic effects due to spin-lattice rel axation at temperatures around 10 K.