FEMTOSECOND TRANSIENT ABSORPTION-SPECTROSCOPY OF A SPIROOXAZINE PHOTOCHROMIC REACTION

The dynamics of C-O bond cleavage followed by the structural change to merocyanine in the photochromic reaction of a spirooxazine derivative has been studied by femtosecond transient absorption spectroscopy. Within 2 ps after excitation, the very broad spectra assigned to the absorption of the transition state, following the S(n) <-- S1 absorption spectrum of spirooxazine, were observed. The rate constants of C-O bond cleavage and the relaxation from the transition state to a metastable merocyanine were estimated to be approximately (700 fs)-1 and (470 fs)-1, respectively.