Dynamics of excited m-dichlorobenzene is investigated in real time by femtosecond pump-probe method, combined with time-of-flight mass spectrometric detection in a supersonic molecular beam. The yields of the parent ion and daughter ion C6H4Cl+ are examined as a func-tion of the delay between the 270 and 810 nm femtosecond laser pulses, respectively. The life-time of the first singlet excited state S1 of m-dichlorobenzene is measured. The origin of this daughter ion C6H4Cl+ is discussed. The ladder mechanism is proposed to form the fragment ion. In addition, our experimental results exhibit a rapid damped sinusoidal oscillation over interme-diate time delays, which is due to quantum beat effects.
