Ultrafast absorption spectroscopy of photodissociated CF2Br2: Details of the reaction mechanism and evidence for anomalously slow intramolecular vibrational redistribution within the CF2Br intermediate

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Abstract
Ultrafast time‐resolved absorption spectroscopy in the hard ultraviolet has been used to investigate the photodissociation of gas‐phase CF2Br2 photolyzed at 248 nm. The broadband spectra obtained in the 250–265 nm region have shown that absorption of a single photon activates a two‐step sequential elimination of the molecule’s two bromine atoms, leaving the product CF2 radical in the ground or first‐excited vibrational state of its ν2 bending mode. The spectra also demonstrate the direct detection of the vibrationally hot CF2Br intermediate species itself. We interpret the ∼6 ps time scale over which the diffuse CF2Br spectrum evolves as evidence for slow intramolecular vibrational redistribution within this molecule.