Measurement of spin-lattice relaxation times with longitudinal detection

New experimental schemes to measure spin-lattice relaxation times T₁ on the basis of inversion-recovery and saturation-recovery experiments with longitudinal detection are introduced. With this approach, paramagnetic species with T₁ values as short as 20 ns can be measured. Possibilities to reduce unwanted signals and instrumental artifacts are analyzed. An experiment where the signal is induced directly by the time-dependent M₂ magnetization is also proposed. Experimental results for organic radicals and defect centers are presented and compared with data obtained with conventional techniques, and a metal complex at 250 K is analyzed where it is very difficult to get information about relaxation times with established methods because of fast spin-spin relaxation.