Photoionization and dissociation of BF3·((CH3)2O)n mixed aggregates (n=1, 2) studied by mass spectrometry and ab initio calculations

Upon photoionization of mixed aggregates of boron trifluoride and dimethyl ether, strong intermolecular and intramolecular fragmentation is observed. The complexes and their fragments show similar appearance energies; they exceed considerably the adiabatic ionization potentials. Ab initio calculations of the ionic and neutral structures of the aggregates were performed in order to elucidate the ionization and fragmentation behaviour. The mixed aggregates contain neutral BF3·(CH3)2O units which are almost uninfluenced by the aggregation of a second ether molecule. Ionization of the (CH3)2O·BF3 unit leads to intermolecular charge transfer before dissociation or fluorine abstraction to form the cationic singlet molecule (CH3)2OBF2+.