Recombination dynamics of photodissociated I-2(-) in size selected Ar and CO2 clusters

We report time-resolved photodissociation and geminate recombination dynamics of I-2(-) in size-selected I2-Arn and I-2(-)(CO2)(n) cluster ions by using ultrafast pump-probe techniques at 790 nm in conjunction with a tandem time-of-flight mass spectrometer. The absorption recovery, which reflects the time scale for photodissociation followed by recombination and vibrational relaxation of I-2(-) inside the cluster, shows a strong dependence on the composition of the surrounding cluster solvent. The absorption recovery time for I-2(-)(CO2)(16) is similar to 1 ps, whereas for I2-Ar20 it is similar to 130 ps. This difference is discussed in terms of electrostatic and hard sphere interactions, We also observe the time dependence of the destruction of the Ar solvent cage for I2-Ar16. Finally, absorption recovery data for I-2(-)(CO2)(n) cluster ions taken with 790 nm pump-probe wavelengths are compared with the greater energy release 720 nm data. (C) 1997 American Institute of Physics.