Ultrafast control of the LnF + /LnO + ratio from Ln(hfac) 3 .

The photo-induced dissociative ionization of lanthanide complexes Ln(hfac) 3 (Ln = Pr, Er, Yb) is studied using ultrafast shaped laser pulses in a time-of-flight (TOF) mass spectrometry setup. Various fluorine and Ln-containing mass fragments were observed, which can be interpreted by the photo-fragmentation mechanistic pathway involving C-C bond rotation processes proposed previously. A set of experiments used pulse shaping guided by closed-loop feedback control to identify pulses that optimize the ratio of LnF + /LnO + . In agreement with previous studies in which very little LnO + was observed, broad pulses were found to maximize the LnF + /LnO + ratio, which involves metal-ligand bond-breaking followed by bond rotation and bond rearrangement. In contrast, a transform limited (TL) pulse favored the formation of LnO + . Finally, the recently developed experimental control pulse slicing (CPS) technique was applied to elucidate the dynamics induced by fields that either maximize or minimize the LnF + /LnO + ratio, which also indicates that longer laser pulses facilitate LnF + formation during the C-C bond rotation dissociative-ionization process.