Dynamics of Excited o-Dichlorobenzene

The dynamics of the first excited singlet electronic state (S-1) of o-dichlorobenzene was investigated in real time by the femtosecond pump-probe method combined with time-of-flight mass spectroscopy and the photoelectron velocity mapping technique. The lifetime of the S-1 vibrational ground state was determined experimentally to be (651 +/- 10) ps, corresponding to the intersystem crossing process from the S-1 state to the triplet state. Two decay channels were found in the S-1 vibrationally excited mode 9a(2)18a(2). The fast process (lifetime constant (458 +/- 12) fs) is because of the internal conversion from the S-1 vibrationally excited mode to the highly vibrationally excited ground state (S-0). The slow process (lifetime constant (90 +/- 10) ps) is attributed to the intersystem crossing process from the S-1 state to the triplet state (T-1). Photoelectrons with long lifetime characteristics in the spectrum might be connected with the intersystem crossing process. Enhanced spin-orbital coupling in the S-1 highly vibrationally excited state accelerates the intersystem crossing process