ENHANCED PRODUCTION OF UNPROTONATED HYDROGEN-BONDED CLUSTER IONS

A novel technique is described which may be employed in mass spectrometry for the efficient production of unprotonated hydrogen-bonded cluster ions. Using the pick-up technique, clusters of the species to be investigated are embedded in large Ar(x) host clusters and carried by them to the ion source. The argon atoms constituting the substrate cluster are evaporated upon ionization and argon-free cluster ions can be obtained. Owing to the efficient transfer of the excess energy from the excited molecular cluster ion to the substrate cluster, the commonly encountered protonation reaction is considerably quenched, thus leading to the production of unprotonated species. The new technique is demonstrated for the generation of (CH3F)n+ and (CH3OH)n+ cluster ions with n = 2 or 3.