Figure 3. Power-saturation measurement of spin lifetimes.

(a) Schematic of the Bruker ER 4122SHQE cavity with microwave magnetic and electric fields in-plane and out-of-plane, respectively. Plot insets show the magnetic field strength across the cavity. We account for the vertical distribution of B₁ and minimize horizontal variations by confining our samples to a diameter of 1 mm. (b) Power saturation of the integrated ESR absorption spectra for the series of molecules with fitted curves to extract T₁ and T₂. (c) Evolution of derivative ESR spectrum with increasing microwave powers for the example of L-C12-DTBTBT.