Ultrafast dissociation dynamics of [Fe(CO)5](n) clusters induced by femtosecond IR radiation

Using the femtosecond time-resolved infrared pump-visible probe technique, we have measured for the first time the ultrafast dissociation dynamics of [Fe(CO)5]n clusters induced by IR resonant excitation of C≡O vibrational modes in the 5-μm region. Free Fe(CO)5 molecules formed as a result of the cluster dissociation have been ionized by the femtosecond laser radiation at λ = 400 nm and have been detected with a time-of-flight mass-spectrometer. The temporal dependence of the yield of free molecules has been measured under different conditions of the IR laser excitation. We have proposed a model that describes well experimental results and makes it possible to calculate the temporal profile of the cluster temperature in terms of the concept of the evaporative ensemble. The rates of the intramolecular and intracluster vibrational relaxation in [Fe(CO)5]n clusters have been estimated.