Gas-phase thermochemistry of the group 3 dioxides: ScO_2, YO_2 and LaO_2

Abstract

Gas-phase ScO_2, YO_2, LaO_2 and the singly charged cations of these species are formed in endothermic reactions between MO+ (M=Sc, Y, and La) and NO_2 in a guided ion beam mass spectrometer. The cross sections of these reactions are measured as a function of kinetic energy and are interpreted to give the following 0 K bond energies (in eV): D^0(OScO)=3.95±0.33, D^0(OYO)=4.14±0.22, D^0(OLaO)=4.20±0.33, D^0(OSc^+O)=1.72±0.19, D^0(OY^+O)=1.76±0.16, and D^0(OLa^+O)=0.99±0.31. Values for the MO_2 ionization energies (in eV) are determined to be IE(ScO_2)=8.66±0.20, IE(YO_2)=8.23±0.16 and IE(LaO_2)=8.11±0.35. The differences between these values and estimates in the literature are discussed by considering the nature of the bonding in MO_2 and MO^+_2.

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