Femtosecond high-resolution pump-probe experiments have been used together with theoretical ab initio quantum calculations and wave packet dynamics simulations to decode an optimal femtosecond pulse that is generated from adaptive learning algorithms. This pulse is designed to maximize the yield of the organometallic ion CpMn(CO)3 while hindering the competing fragmentation. The sequential excitation and ionization of the target ion are accomplished by an optimized field consisting of two dominant subpulses with optimal frequencies and time delays.

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The electronic and geometric structures of η5-CpMn(CO)3 in the near-UV region are investigated through CASSCF/CASPT2 and TD-DFT methods. The optimized geometries obtained at different levels of calculation are compared to the crystal and gas-phase structures for the electronic ground state. The change of geometry when going from the electronic ground state to the low-lying excited states was analyzed on the basis of gradient-CASSCF calculations. The lowest excited-state bA‘ corresponding to a 3dMn → 3dMn excitation calculated at 25 733 cm-1 (3.22 eV) and the d1A‘ calculated at 30 366 cm-1 (3.80 eV) with very low oscillator strengths (<0.007) do not show any significant geometry changes with respect to the electronic ground state. The main geometry changes which never exceed 10% correspond to elongations of the Mn−Cp and Mn−CO bonds (with the out-of-plane CO ligands). The c1A‘ (3dMn → 3dMn) absorbing state calculated at 26 470 cm-1 (3.31 eV) with an oscillator strength of 0.0157 is characterized by an elongation of the Mn−COax bond (COax being the in-plane carbonyl) and does not converge to a minimum, which is a characteristic of dissociative states. Among the 1A‘ ‘ (3dMn → 3dMn) states calculated between 24 972 and 29 949 cm-1 only the lowest one has an oscillator strength exceeding 0.01. The metal to ligand charge transfer (MLCT) states (3dMn → π*CO) are calculated between 37 410−45 019 cm-1 and are well separated from the metal centered (MC) (3dMn → 3dMn) states (≈1.0 eV). The time-dependent DFT excitation energies and related assignments compare rather well to the multistate-CASPT2 results as far as the lowest MC excited states are concerned.