Photodissociation of indium oxide cluster cations

Indium oxide cations of the form InnOm+ are produced by laser vaporization in a pulsed nozzle source and detected with time of flight mass spectrometry. The In2O+ and In3O+ ions have high relative intensities in the mass spectra of clusters sampled directly from the source. Cluster cations are mass-selected and photodissociated using the third harmonic (355 nm) of a Nd:YAG laser. The elimination of indium cation is the dominant loss channel for all cluster cations. However, certain other clusters, i.e., In2O+, In2O2, In3O+ and In3O2+ are produced as fragments from several cluster sizes and are thus identified as particularly stable. Density functional theory calculations are employed for selected species to determine their structures and relative stabilities. The Wade–Mingos electron counting rules are found to be inappropriate for these systems because their bonding is primarily ionic.

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► Indium oxide cluster cations are produced in a laser vaporization source and analyzed with time-of-flight mass spectrometry.
► Cluster ions are mass-selected and photodissociated at 355 nm. Prominent photofragments are In+, In2O+, In2O2, In3O+ and In3O2+.
► Density functional theory finds linear structures for many small clusters and confirms the relative stabilities of prominent photofragments.