PHOTOEXCITED EOSIN AS AN EPR SPIN-PROBE

Photoinduced spin triplets usually exhibit high spin polarization, whi ch exceeds by orders of magnitude the equilibrium spin polarization fo und at room temperature. Equivalently, one may speak of a cryogenic ef fective 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 normall y 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.