IDENTIFICATION OF CLUSTERS PRODUCED IN AN ATMOSPHERIC-PRESSURE IONIZATION PROCESS BY A COLLISIONAL DISSOCIATION METHOD

Many kinds of clusters were observed even in pure nitrogen gas streams by atmospheric pressure ionization (API). The spectra were changed drastically with residual water concentration in the stream. The observed ion species were investigated by a collisional dissociation method which was successfully applied to clarify the molecular composition of clusters. Clusters having weak cluster bonds dissociated in an electric field at about 1 Torr through multiple collisions. The order of cluster dissociation was dependent on cluster bond strength. The dissociation patterns were used to clarify the cluster compositions. As a result, it appeared that many kinds of clusters such as H3O+OH, H2O+N2, H3O+N2, H2O+N2-N2, N3+H2O, etc. were produced in the API process. The drift electric field strength critical for cluster dissociation was closely related to the cluster bond strength and number of cluster vibrations. The observed drift voltages critical for cluster dissociation were compared with the reported cluster bond strengths. © 1979, American Chemical Society. All rights reserved.