Determine quintet-manifold spin-lattice relaxation rates in the pentacene dimer

Determine the spin–lattice relaxation rates between the sublevels of the quintet multiexciton manifold 5(TT)m (in particular transitions involving m=0 and m=±1) generated by intramolecular singlet fission in a pentacene dimer, and ascertain whether these rates are asymmetric, since specific parameters for this molecule are currently unavailable and are often assumed by analogy to pentacene monomers.

Background

Accurate modeling of singlet-fission-born quintet states in pentacene dimers requires knowledge of spin–lattice relaxation rates between quintet sublevels. Asymmetric relaxation among sublevels has been reported or suggested in related systems, but concrete rate parameters for the specific pentacene dimer studied here are not available. Lacking these data, the analysis assumes rates comparable to those of pentacene monomers for certain transitions.

Determining these rates—and whether they are asymmetric—would refine Lindblad-based simulations of ODMR and dynamical decoupling protocols, improve predictions of photoluminescence contrast and coherence dynamics, and guide the design of high-sensitivity molecular quantum sensors based on quintet multiexciton states.

References

Asymmetric spin lattice relaxation rates might be present also in the quintet manifold [19], but unfortunately we could not find parameters in the case of the molecule under investigation.

— Quantum Sensing with Triplet Pair States: A Theoretical Study  (2603.29509 - Concilio et al., 31 Mar 2026) in Spin systems and methodology (Section), paragraph discussing relaxation rates of the quintet manifold (before Table 1)