Probing ultrafast internal conversion of o-xylene via femtosecond time-resolved photoelectron imaging

The dynamics of excited states in o-xylene molecules has been studied by femtosecond time-resolved photoelectron imaging coupled with time-resolved mass spectroscopy. The ultrafast internal conversion from the S-2 state to the vibrationally hot S-1 state on timescale of 60 fs is observed on real time. The secondarily populated high vibronic S-1 state deactivates further to the S-0 state on timescale of 9.85 ps. Interestingly, the lifetime of the low vibronic S-1 state is much longer, extrapolated to similar to 12.7 ns. The great differences of lifetime of different vibronic S-1 state are due to their different radiationless dynamics. (C) 2010 Optical Society of America