Analysis and control of laser induced fragmentation processes in CpMn(CO)3

In this paper we present experimental and theoretical findings about the dynamics of ultrafast fragmentation processes which occur during resonant multiphoton ionization of CpMn(CO)(3) with femtosecond laser pulses. Employing a two-color pump and probe scheme, it was possible to retrieve lifetimes of the electronically excited parent molecule and its first fragment CpMn(CO). The observed time of 66 fs for the loss of the first CO-ligand is in good agreement with the results of one-dimensional quantum dynamical model simulations based on three relevant adiabatic ab initio potentials and the related components of the transition dipole matrix elements, in C, symmetry. Subsequently, smaller fragments appear somewhat later during approximately 100 fs, Based on these findings we performed feedback control experiments on the system in order to optimize individual fragmentation/ionization paths. With the routine a considerable increase of - for example - the CpMn(CO)(+)/CpMn(CO)(3)(+) intensity ratio was achieved. The obtained optimized laser pulses correlate well with the fast dynamics of the photoinduced preparation of CpMn(CO); versus CpMn(CO)- product ions, respectively. (C) 2001 Published by Elsevier Science B,V.