Predissociation dynamics of I2(B) in liquid CCl4 observed through femtosecond pump-probe measurements: Electronic caging through solvent symmetry

Direct observations of the solvent induced electronic predissociation of I2(B) in liquid CCl4 are made using femtosecond pump–probe measurements in which fluorescence from spin–orbit excited I*I* pairs, bound by the solvent cage, is used as detection. Data is reported for initial preparations ranging from the B state potential minimum, at 640 nm, to above the dissociation limit, at 490 nm. Analysis is provided through classical simulations, to highlight the role of solvent structure on: recombination, vibrational relaxation, and decay of coherence. The data is consistent with an anisotropic I2(X)–CCl4 potential which, in the first solvent shell, leads to an angular distribution peaked along the molecular axis. The roles of solvent structure and dynamics on electronic predissociation are analyzed. The data in liquid CCl4 can be understood in terms of a curve crossing near v=0, at 3.05 Å