Photodissociation of (ICN)(2) van der Waals dimer using velocity imaging technique

Photodissociation of (ICN)(2) dimer from 265 to 270 nm are studied using time-of-flight mass spectrometry combined with velocity imaging technique. Both I(+) and I(2) (+) ions are found in the mass spectra. The I(2) (+) ions result from (1+1) resonant ionization of the neutral I(2) fragment that is produced in the photodissociation of dimer, but not from dissociative ionization of (ICN)(2); i.e., (ICN)(2) (+)+hnu-->I(2) (+)+2CN. The dissociation channels of I(2) (+) leading to I(+) are all found with parallel character. The total kinetic energy distributions and anisotropy parameters of the I(+) channels produced by (ICN)(2) are almost the same as those from a neutral I(2) sample, thereby confirming that the I(2) fragments are obtained in cold state. With the aid of ab initio calculations, a plausible dissociation mechanism is proposed.