Collision-induced dissociation of [UO (NO )(O )] and reactions of product ions with H O and O.

We recently reported a detailed investigation of the collision-induced dissociation (CID) of [UO (NO ) ] and [UO (NO ) (O )] in a linear ion trap mass spectrometer (J. Mass Spectrom. DOI:10.1002/jms.4705). Here, we describe the CID of [UO (NO )(O )] which is created directly by ESI, or indirectly by simple elimination of O from [UO (NO )(O ) ] . CID of [UO (NO )(O )] creates product ions as at m/z 332 and m/z 318. The former may be formed directly by elimination of O , while the latter required decomposition of a nitrate ligand and elimination of NO . DFT calculations identify a pathway by which both product ions can be generated, which involves initial isomerization of [UO (NO )(O )] to create [UO (O)(NO )(O )] , from which elimination of NO or O will leave [UO (O)(O )] or [UO (O)(NO )] , respectively. For the latter product ion, the composition assignment of [UO (O)(NO )] rather than [UO (NO )] is supported by ion-molecule reaction behavior, and in particular, the fact that spontaneous addition of O , which is predicted to be the dominant reaction pathway for [UO (NO )] is not observed. Instead, the species reacts with H O, which is predicted to be the favored pathway for [UO (O)(NO )] . This result in particular demonstrates the utility of ion-molecule reactions to assist the determination of ion composition. As in our earlier study, we find that ions such as [UO (O)(NO )] and [UO (O)(O )] form H O adducts, and calculations suggest these species spontaneously rearrange to create dihydroxides.