Ultrafast Dissociation Dynamics of [Fe(CO)₅]_n Clusters Induced by Femtosecond IR Radiation

Abstract

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.

Ultrafast Dissociation Dynamics Induced in [Fe(CO)5]nXem Mixed Clusters by Resonant Femtosecond Infrared Laser Radiation

“…In principle, there is no way to form lots of neutral Xe atoms with multi-electron-volt kinetic energy from mixed clusters by IR pump pulse only. Indeed, if we assume that the mixed cluster has, for example, 100 molecules in the core, an estimate for the absorbed energy gives us a value of less than one absorbed IR quantum per molecule. It means that we only deliver less than 25 eV to the whole cluster.…”

“…In our work, we studied the ultrafast dissociation dynamics of homogeneous [Fe­(CO) 5 ] n clusters induced by IR resonant excitation of CO vibrational modes in the 5 μm range using a femtosecond time-resolved infrared pump–visible probe technique. Free Fe­(CO) 5 molecules formed as a result of cluster dissociation were ionized by femtosecond laser radiation with λ = 400 nm and were detected using a time-of-flight mass spectrometer.…”

STRUCTURAL DYNAMICS OF FREE MOLECULES AND CONDENSED STATE OF MATTER. Part II. TRANSIENT STRUCTURES IN CHEMICAL REACTIONS

“…Photoprocesses induced by resonant vibrational excitation were studied in free Fe(CO) 5 and its molecular clusters [113,114]. Intense femtosecond pulsed radiation in the region of 5 µm was used to excite the intense vibrational bands (the ν 6 and ν 10 modes) of the CO-bonds of Fe(CO) 5 .…”

“…The yield of free molecules from clusters is determined by the magnitude of the energy absorbed by the cluster, and its temporal dependence is described by a sequential evaporation of molecules ( Fig. 13) [113].…”

“…Two relaxation schemes are shown: singlebathmode scheme (k 1 ′) and sequential two-bath-mode scheme (k 1 and k 2 ). From ref [113]…”