SPIROOXAZINE PHOTOCHROMISM - PICOSECOND TIME-RESOLVED RAMAN AND ABSORPTION-SPECTROSCOPY

Photochromatic reactions in three spirooxazine compounds based on the formation of merocyanine isomers are examined by picosecond time-resolved resonance Raman and absorption spectroscopies. Each spirooxazine is excited with 287 nm dye laser pulses (35 ps fwhm) while resonance Raman scattering from the merocyanine isomer(s) formed by ring opening is generated with 575 nm laser excitation into the resultant delocalized, π-electron absorption system. Vibrational resonance Raman spectra of the merocyanine isomer(s) recorded over the 50 ps-1.5 ns interval do not change, indicating that both ring opening to form a stable merocyanine isomer or distribution of isomers is complete within 50 ps and that this isomer(s) distribution formed remains unchanged for at least 1.5 ns. © 1990.