Ultrafast imaging of electronic relaxation in o-xylene: a new competing intersystem crossing channel

Abstract

The ultrafast dynamics of the second singlet electronically excited state (S₂) in o-xylene was investigated by femtosecond time-resolved photoelectron imaging. A new competing relaxation channel of the S₂ state was observed and assigned to the T₃ ← S₂ intersystem crossing. Interestingly, it is found that the relaxation via this channel occurs on a comparable femtosecond timescale as the S₁ ← S₂ internal conversion. A lifetime of ∼60 fs for the initially excited S₂ state, of 540 (±17) fs for the secondary populated S₁ state, and of 7.23 (±0.21) ps for the T₃ state could be inferred.