RESTRICTED DIFFUSION, RELAXATION AND ABSOLUTE MAGNETIC-SUSCEPTIBILITYOF THE CONDUCTION ELECTRONS IN QUASI-ONE-DIMENSIONAL ORGANIC CONDUCTORS

Pulsed electron spin resonance (ESR) is conveniently used for the anal ysis of spin dynamics in organic conductors - e.g. the derivation of s pin-spin (T-2) and spin-lattice (T-1) relaxation times. If, in additio n to the homogeneous magnetic field, a field gradient is applied, the diffusion constant (D) of the conduction electrons can be determined f rom the analysis of the echo decay. We show that restricted diffusion can be identified by analysis of the echo decay with help of Neuman's equations. An average diffusion length of 95.8 mu m has been obtained for a Fluoranthene radical cation salt. For appropiate choice of the t ipping angles, multiple spin echos can be observed after two excitatio n pulses, caused by the nonlinearity of the Bloch equations. We show f or Fluoranthene and Perylene radical cation salts that their quantitat ive analysis allows the derivation of the conduction electrons' absolu te magnetic susceptibility without sensitivity calibration of the spec trometer.