Ultrafast dissociation dynamics of ferrocene and [3]-ferrocenophan

We present pump-probe results for ferrocene and [3]-ferrocenophan measured with two 200-fs UV laser pulses of different wavelengths. The molecules are excited by single-photon absorption to a fast decaying intermediate state and ionized by absorption of a second photon. The so-produced parent cation s can absorb further photons until their internal energy is sufficient to o pen different fragmentation channels. Because of the broad absorption spect ra of ferrocene, each laser pulse can act as a pump and probe pulse. We use the rotating wave approximation of the Schrodinger equation of a three-lev el system to numerically calculate the population dynamics of the neutral e xcited state, the parent ion, and the fragment ions produced after absorpti on of further photons in the ferrocene cation. From the observed transients in the ferrocene cation signal, a dissociation time of 200 fs of the neutr al excited ferrocene is found and the same dissociation time is measured fo r [3]-ferrocenophan, where the rings are bridged. This points to a concerte d, multiple metal-ligand bond break after photon absorption, which is not h indered by the bridge. From a comparison of measured and calculated transie nts in the fragment ion signal, we conclude that the observed fragment ions originate from a dissociation of the ferrocene cation rather than from a n eutral dissociation and 'subsequent ionization.