Figure 6.

Orientational dependence of the resonant magnetic field for the electron spins in the triplet state of (a) the NV ${}^{-}$ center and (b) pentacene doped in benzoic acid at a microwave frequency of 11.66 GHz. The $x$ , $y$ , and $z$ axes represent the principal axes of the ZFS tensor. (c) Orientational dependence of the polarization of the electron spins in the photo-excited triplet state of pentacene doped in benzoic acid in 0.39 T calculated from the zero-field population . The upper and lower rows correspond to the EPR transitions between the $m_S=+\mathrm{1}$ and $m_S=\mathrm{0}$ states and between the $m_S=\mathrm{0}$ and $m_S=-\mathrm{1}$ states, respectively. The regions between the black lines correspond to the orientations for which the crystallites experience polarization transfer by the ISE using the optimized field-sweep range found in the experiments demonstrated in Fig. .