Summary: dophila was determined to be 61 fs (11).
The carotenoid in this complex, rhodopin
glucoside, like lycopene has 11 conjugated
double bonds. If we take the time scale for
the S2 to Sx transition from this report, then
at least some of this energy transfer must
involve Sx. Indeed, if S2 was the only state
from which energy transfer could occur,
then the efficiency would be expected to be
much lower than the measured value of this
LH2 complex, which is 50%. This report
illustrates again the remarkable subtlety of
the photophysical behavior of carotenoids.
The exact electronic designation of Sx and
its involvement in the molecular mecha-
nisms of carotenoid-to-chlorophyll singlet-
singlet energy transfer remain to be
References and Notes
1. O. Isler, Carotenoids (Birkhauser-Verlag, Basel, 1971).