Collision-induced dissociation of protonated nanodroplets

Protonated nanodroplets are easily generated using electrospray ionization mass spectrometry (ESI–MS) and may be isolated and fragmented using collision-induced dissociation (CID), causing sequential loss of water molecules. These studies reveal not only the expected high stability of the “magic” protonated water cluster [H(H2O)21]+, a dodecahedral clathrate cage, but also a new, rather more subtle trend in stabilities of product ions that manifests itself as increased stability of clusters that have a multiple of 12–13 water molecules.