Switched external magnetic field (SEMF) CIDNP — a new technique for investigation of the spin dynamics and kinetics of short-lived reaction intermediates in weak magnetic fields

A new time-resolved technique is described to study low magnetic field CIDNP kinetics. The switched external magnetic field (SEMF) CIDNP involves fast switching of a magnetic field during the lifetime of radical intermediates. The information about the spin dynamics and chemical kinetics is obtained from the effect of the magnetic field switch on nuclear polarization of the diamagnetic products of radical reactions. The method has been used to measure the rate constants of a degenerate electron exchange reaction and to provide information on electron polarization in chemical reactions performed in weak magnetic fields.