In eq.( ), 𝐸 9 ! ' ()$ is obtained by diagonalizing 𝑯 -()$ . For the EPR transitions in 2 (TD)m in eq.( ), As a result, delay time dependence of the transient EPR spectrum is computed as shown by the red lines (Fig. ) with employing deactivation rate constant of kREC = 0.5 ns -1 from the restricted anisotropic motion at the cryogenic conditions. When the thermal energy (kBT) is smaller than the exchange coupling (3|J|) in Fig. , the 2 |TD> -> 4 |TD> conversion would obey the Fermi's golden rule expression to generate the spin polarization by the intersystem crossing. Spin polarization mechanism by the zero-field splitting interaction: It is noteworthy that no perturbation approach is required when the present ZFS-induced 2 |TD>-4 |TD> conversions are considered in Fig. , while the perturbation approach considering a very weak admixture of the higher-lying excited states (Sn-D0 state, as an example) is essential to gain the SOC contribution via the orthogonal orbital configuration (n-orbital character in the Sn state) for the spin conversion. Therefore, the ZFS effect is likely to be dominant for the quartet polarization when the molecular conformation motions are involved on the metal-free chromophores in the fluid environment. For deeper understandings of the spin polarization mechanism by the activation processes at room temperature, we consider how the anisotropic ZFS play a role. Table shows calculated matrix elements of nm𝑄 P 3 n𝑯 -𝑻𝐃𝟐 n𝐷 P pn for two different magnetic field directions of (q, f) = (1, 0) degrees and (q, f) = (p/2, 0) in the activated TD2 state. From eq.( ), these non-zero doublet-quartet interactions will produce the doublet-quartet coherences (𝜌 9 !" ) ! ()$