Figure 4.

(a–c) Optimization of the ISE pulse sequence for microdiamonds (upper row, filled circles) and pentacene-doped benzoic acid (PBA) (lower row, open circles) through adjustment of (a) the field-sweep width $B_{\mathrm{sweep}}^{\mathit{\alpha }}$ , (b) the microwave duration $t_{\mathrm{MW}}^{\mathit{\alpha }}$ , and (c) the microwave intensity ${\mathit{\omega }}_{\mathrm{1},\mathrm{e}}^{\mathit{\alpha }}$ , where $\mathit{\alpha }=\mathrm{NV},\mathrm{P}$ for microdiamonds and PBA, respectively. The values of the fixed parameters are indicated in each graph. The gray lines in (c) indicate the ${}^{\mathrm{13}}$ C Larmor frequency for the magnetic field that corresponds to the low-field horn of the EPR spectrum. (d) Longitudinal relaxation (upper graph) and lifetime decay (lower graph) of the electron spins in the triplet state of NV ${}^{-}$ centers in microdiamonds and pentacene, respectively.