Geometrical Structures of Gas-Phase Cerium Oxide Cluster Cations after Reaction with Nitric Oxide Studied by Ion Mobility Mass Spectrometry.

Cerium oxide cluster cations were reacted with nitric oxide molecules and then measured by ion mobility mass spectrometry (IMMS). Ce n O 2 n +1 N + species appeared as products of the reaction Ce n O 2 n + + NO → Ce n O 2 n +1 N + , and their collision cross sections (CCSs) with helium were obtained by IMMS. The experimental CCSs of Ce n O 2 n +1 N + were 2-6 Å 2 larger than those of Ce n O 2 n + for n = 4-10. Geometrical structures of Ce 4 O 9 N + and Ce 5 O 11 N + were assigned by comparing experimental CCSs with theoretically calculated CCSs of candidate structures. The suggested structures showed that the adsorbed NO molecule is oxidized by the Ce n O 2 n + cluster into a nitrite (NO 2 - ) or nitrate (NO 3 - ). The Ce n O 2 n +1 N + species are regarded as intermediates of the NO oxidation reaction Ce n O 2 n + + NO → Ce n O 2 n -1 + + NO 2 , and therefore, the present results are helpful for understanding redox reactions involving gas-phase Ce n O 2 n + cluster ions.