Figure 4. Transient absorption decays for a ~1 X 10^-4 M solution of 1 at 77 K in a 2-methyltetrahydrofuran glass. Excitation was with a ~5-ns, 590-nm laser pulse. (a) Decay at 700 nm of the fullerene triplet state (C-P-³C₆₀). The smooth curve is an exponential decay with a time constant of 81 m s. (b) Decay of the carotenoid and fullerene radical ions at 980 nm (the smooth curve is the sum of two exponential decays of 1.5 m s (73%) and 7 m s (27%)), and rise of the carotenoid triplet state monitored at 550 nm (the smooth curve has a rise time of 1.4 m s). (c) Rise and decay of the carotenoid triplet absorption at 550 nm. The smooth curve is the sum of a 1.4 m s rise time and decay times of 10 m s (87%) and 83 m s (13%).