Ion imaging studies of the photodissociation dynamics of CH2I2 at 248 nm

The photodissociation of CH2I2 at 248 nm is investigated using velocity map ion imaging with photoionization detection of the I∗ (2P1/2) products. The velocity distribution of the I∗ products reveals that only a small fraction of the available energy is released as translational energy, consistent with a simple impulsive model. Most of the excess energy is channeled into internal excitation with 〈 E int 〉 = 36.3 kcal mol−1 for CH2I radical fragments produced with I∗ atoms. The anisotropy angular distribution of the I∗ fragments and corresponding positive anisotropy parameter are indicative of prompt dissociation and electronic state mixing.