Optimization of Two-Stage Measurements of T₁

A recent analysis of the optimization of adaptive T₁ measurements based on inversion-recovery (IR) experiments is extended to allow for the use of fast-inversion-recovery (FIR) experiments in either of the two stages of the experiment. FIR experiments can be carried out more quickly than IR experiments but individual measurements are inherently less precise. Both types of experiments are considered, with a fixed number of times at which measurements are made and with a fixed total running time. The results of the investigation suggest that an optimal two-stage experiment with a fixed number of measurements makes use of the FIR technique in the first stage and IR in the second. When the total running time is fixed, it is generally better to use FIR in both stages.