The role of the newly-found 1Bu- state of carotenoid in mediating the 1Bu+-to-2Ag- internal conversion and the excited-state dynamics of carotenoid and bacteriochlorophyll in a bacterial antenna complex

Most recent finding of the 1Bu- state of carotenoids in-between the 1Bu+ and 2Ag- states by measurements of resonance-Raman excitation profiles, and that of the 1Bu+-1Bu--2Ag- internal-conversion processes by visible and near-infrared time-resolved absorption spectroscopy are reviewed for all-trans-neurosporene both free in solution and bound to the LH2 antenna complex from Rhodobacter sphaeroides G1C. The excited-state reactions between carotenoid (Car) and bacteriochlorophyll (BChl) a in the LH2 complex, including the singlet hetero-fission between them and the Car-to-BChl singlet-energy transfer, both probed by time-resolved absorption spectroscopy, are also summarized.