Photo-induced reactions of CH2I2 in solution studied by the ultrafast transient absorption spectroscopy

We have studied the photo-induced reactions of CH2I2 upon excitation at 268 nm in CH3CN by femtosecond transient absorption spectroscopy. The time profile of transients observed at 400 nm consists of three components: fast rise (200 fs), fast decay (500 fs), and slow rise (7–13 ps). The first two components are independent of the solute concentration and are assigned to the photofragment CH2I radical. The slow rise becomes faster by increasing concentration and is assigned to the formation of a charge-transfer complex between the photofragment I and CH2I2 in solute aggregate. This is followed by full electron transfer from CH2I2 to I forming CH2I2+.