Vacuum ultraviolet photoionization and photodissociation of ferrocene

Abstract

Photoionization and photodissociation of ferrocene [Fe(C 5H 5) 2] is examined by using vacuum ultraviolet (VUV) photons from a synchrotron radiation source and a time-of-flight (TOF) photoionization mass spectrometer. VUV absorption by ferrocene results in Fe(C 5H 5) 2 ·+, FeC 5H 5 +, FeC 3H 3 +, Fe ·+ and C 10H x ·+ (x = 8 − 10). The dependency of the product distribution on photon energy indicates sequential elimination of C 5H 5· ligands as a major dissociation channel, but concerted elimination of two C 5H 5· ligands also takes place to a lesser degree. Through analysis of TOF peak shape, it is found that Fe(C 5H 5) 2 ·+ molecular ion dissociates into FeC 5H 5 + and C 5H 5· via two channels. One is nonstatistical dissociation with a fast rate, and the other is slow unimolecular decay that becomes more discernible at low photon energy. The rate of unimolecular decay, exemplified by a value of k = 2.4 ± 1.0 × 10 6 s −1 at photon energy of 14.76 eV, is well in accord with the RRKM rate.