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Using nanosecond laser excitation the (beta) -carotene S1 emission has been detected in several solvents at room temperature and 77 K. The S1 fluorescence spectrum was recorded in the near IR from 660 to 1250 nm. Time-resolved single photon counting with picosecond resolution confirmed the S1 state origin of the fluorescence, and the detected fluorescence lifetime is close to the known S1 state lifetime (about 10 ps at 293 K and 20 ps at 77 K). The S1 emission vibrational structure in CS2 can be interpreted with the S1 level at 14300 cm-1. The S1 fluorescence quantum yield is about 25 times lower than that of the S2 fluorescence. It is thus about 4 (DOT) 10-6, from which the S1 yields S0 radiative lifetime can be calculated to be about 3 microsecond(s) .© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
