Study of Cluster Anions Generated by Laser Ablation of Titanium Oxides: A High Resolution Approach Based on Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Laser ablation of titanium oxides at 355 nm and ion-molecule reactions between [(TiO2)(x)](-aEuro cent) cluster anions and H2O or O-2 were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source. The detected anions correspond to [(TiO2)(x)(H2O)(y)OH](-) and [(TiO2)(x)(H2O)(y)O-2](-aEuro cent) oxy-hydroxide species with x = 1 to 25 and y = 1, 2, or 3 and were formed by a two step process: (1) laser ablation, which leads to the formation of [(TiO2)(x)](-aEuro cent) cluster anions as was previously reported, and (2) ion-molecule reactions during ion storage. Reactions of some [(TiO2)(x)](-aEuro cent) cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation pathways were observed: (1) elimination of water molecules, (2) O-2 loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain the experimental data.