Abstract
Subpicosecond time-resolved absorption spectra were recorded in the visible region for a set of photosynthetic carotenoids (Cars) having different numbers of conjugated double bonds including neurosporene (n=9), spheroidene (n=10), lycopene (n=11). Anhydrorhodovirin (n=12) and spirilloxanthin (n=13). Singular-value decomposition and subsequent global fitting of the spectral data matrices lead us to a branched kinetic model including both (1) singlet internal conversion in the sequence of 11Bu+ * 11Bu- * 21Ag- * 11Ag-(G), and (2) singlet-to-triplet fission of 11Bu- * 13Ag plus 13Bu, and subsequent triplet internal conversion of 13Ag * 13Bu. With the knowledge of the new internal conversion in Cars, it is very crucial to re-examine the energy transfer pathway from Car to bacteriochlorophyll (BChl) proposed previously.
