Photoexcited EOSIN as an EPR spin probe

Photoinduced spin triplets usually exhibit high spin polarization, which exceeds by orders of magnitude the equilibrium spin polarization found at room temperature. Equivalently, one may speak of a cryogenic effective spin temperature. The spin relaxation properties however still reflect the dynamics of the molecule at room temperature. This allows investigation of room temperature dynamics with a sensitivity normally reached at cryogenic temperatures only. We investigate photoexcited EOSIN embedded in a polymer matrix. The parameters of the triplet spin Hamiltonian are determined from transient nutation EPR experiments at room temperature. The effective spin temperature is found to be 6 K.