American Chemical Society
jz1c03812_si_001.pdf (436.65 kB)

Singlet Triplet-Pair Production and Possible Singlet-Fission in Carotenoids

Download (436.65 kB)
journal contribution
posted on 2022-02-02, 21:43 authored by Dilhan Manawadu, Darren J. Valentine, Max Marcus, William Barford
Internal conversion from the photoexcited state to a correlated singlet triplet-pair state is believed to be the precursor of singlet fission in carotenoids. We present numerical simulations of this process using a π-electron model that fully accounts for electron–electron interactions and electron–nuclear coupling. The time-evolution of the electrons is determined rigorously using the time-dependent density matrix renormalization group method, while the nuclei are evolved via the Ehrenfest equations of motion. We apply this to zeaxanthin, a carotenoid chain with 18 fully conjugated carbon atoms. We show that the internal conversion of the primary photoexcited state, S2, to the singlet triplet-pair state occurs adiabatically via an avoided crossing within ∼50 fs with a yield of ∼60%. We further discuss whether this singlet triplet-pair state will undergo exothermic versus endothermic intra- or interchain singlet fission.