Supplemental Material

S1. Spin Hamiltonian and Simulation Method for ML effects; S2. XRD pattern; S3. Incident light power dependence of F and ML effect; S4. SEM image of the Rb Powder; S5. Matrix elements of Hamiltonian using zero-field and high-field basis sets; S6. kha, kd and krec Dependence of ML Effect; S7. Simulation of ML effect using one-site model; S8. Singlet character and energy for spin state as function of B0.