A pulsed supersonic entrainment reactor for the rational preparation of cold ionic complexes

We describe an ion source for the efficient preparation of cold ion-molecule complexes, X−⋅M. The method relies on condensation of solvent molecules, M, onto argon-solvated ions, X−⋅Arm, where the X−⋅Arm species are formed in a primary expansion and the molecular partner, M, is interfaced to this flow in the hydrodynamic region by supersonic entrainment. This hybrid “supersonic afterglow” reactor provides a clean synthetic approach for both bare and argon-solvated complexes, where the latter are particularly useful since their structures can be characterized by “nanomatrix” infrared predissociation spectroscopy.