We have clarified the electron spin polarization mechanism in a chromophore-radical linked system by the theoretical implementation of the orientation modulation effects of the ZFS and of the Jcoupling (J, D-modulation) by the thermal activations using the density matrix formalism analysis of the SLE. From Fig. , the gigahertz conformation dynamics (k12 and k21) is concluded to play a role on the partial line-shape narrowing in the A/E/A/E pattern spectra of the quartet state. This is well consistent with the recent molecular dynamics studies of the linked chromophores causing the large degrees of the torsional motion in the aromatic molecules at room temperature. However, this gigahertz conformation dynamics will also cause an uncertainty (or inhomogeneity) in the transition energies between Q ±"/$ and Q ±%/$ to induce the decoherence in the EPR transitions due to the Dmodulation. Thus, the reported microsecond coherence time of the quartet in a PDI-TEMPO linked system at 80 K is due to the hindered conformation changes in the triplet PDI moiety, showing the A/E/E/A/A/E pattern (Fig. ). The absence of the D-modulation is also consistent with the large fine-structure splitting exceeding 50 mT in the low-temperature quartet EPR spectra, while the entire splitting of the A/E/A/E spectra is less than 40 mT in Fig. . The gigahertz conformation dynamics however does not contribute to the quantum coherence in the fluid environment. On the other hand, the center sharp peak by the transition between Q &"/$ and Q '"/$ would be applicable to obtain the quantum coherence (i.e. the Rabi oscillation) because this transition is independent of the ZFS.