Femtosecond dynamics of I2(B 3Πu+) in liquids from resonance Raman spectra

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Abstract
The intensity distributions in the overtones of resonance Raman spectra for I2 in liquid CCl4 and Xe are presented for several excitation energies in the bound part of the B 3Π0u+ state. In liquid CCl4, the decrease in intensity with v‘ is monotonous and for all excitation energies similar to that of a free wave packet in the gas phase. A dephasing time shorter than the round trip time of 300 fs and a dephasing process which occurs beyond 3 Å is inferred, in accordance with predissociation to the a or a’ states earlier proposed. The intensity distributions in liquid Xe contain a fast decay and a plateau and the strength of both contributions varies with excitation energy. For low v’ in the B state a predissociation to the B‘ 1Π1u state within 40 fs in the range of internuclear distances between 2.78 and 2.85 Å is observed which is less pronounced for large v’. The wave packet moves undistorted beyond the crossing with the B‘ state up to 3 Å.