Vibrational relaxation and internal conversion in the overlapped optically-allowed and optically-forbidden or vibronic levels of carotenoids: Effects of diabatic mixing as determined by Kerr-gate fluorescence spectroscopy

The time constants of the vibrational relaxation, υ = 2 → υ = 1 and υ = 1 → υ = 0, in the 1 B u + manifold and those of internal conversion from the 1 B u + (0) level, which is isoenergetic (so-called ‘diabatic’) with the 1 B u - vibronic levels in neurosporene and spheroidene and with the 3 A g - vibronic levels in lycopene and anhydrorhodovibrin, were determined by Kerr-gate fluorescence spectroscopy. The time constants of the vibrational relaxation were in the ∼1:2 ratio, and those of internal conversion agreed with the lifetimes of the diabatic counterparts, i.e., the 1 B u - and 3 A g - electronic states, respectively.