FEMTOCHEMISTRY OF THE IODINE ARENE CHARGE-TRANSFER COMPLEX

Femtosecond spectroscopy is used to investigate the ultrafast photochemistry of the I2: arene charge-transfer complex that occurs upon ''citation into the charge-transfer state. We find that the photo-excited complex branches into two different channels within 25 fs. The dominant channel involves breaking up of the I2: arene complex in its constituent molecules, in the other channel the I: arene complex and an iodine atom are formed. From the polarization anisotropy and the absence of fast geminate recombination of the I: arene and atomic iodine fragments we conclude that in the transition state the I2: arene complex is severely distorted. The molecular I2 formed in a separate channel of the reaction recombines with arene to I2: ar in about 10 ps.