Picosecond time-resolved resonance Raman spectroscopy and vibrational analysis in spirooxazine photochromism

Picosecond time-resolved resonance Raman (TR3) spectroscopy was used to stu dy the dynamics and structure of transient species involved in the photochr omic process in solution of 1,3,3-trimethylspiro[indoline-naphthoxazine]. T R3 spectra recorded in n-hexane, at 10 ps and 50 ps time-delays were compar ed with those obtained on the ns-ms timescale and to the resonance Raman sp ectrum of a permanent opened form. These data and the results of a detailed ab initio vibrational analysis, have allowed us to determine the structure of the transoid isomer already present at 10 ps and to precise the photoch romic mechanism.