FLUORESCENCE EXCITATION SPECTROSCOPY OF MOLECULAR IONS IN A FREE JET EXPANSION

Abstract

Two-photon photoinization is used to generate radical cations from molecules seeded into a free jet expansion of an inert carrier gas. Subsequent absorption by the cations of the output of a tunable dye laser is detected by monitoring the total fluorescence from the beam. The ions are found to be extensively cooled through collisions with the carrier gas. Clusters between the ions and carrier gas atoms have also been observed. The development of an instrument to identify these clusters by mass spectroscopy, and characterize them by laser spectroscopy will be described. The investigation of such clusters provides a means of probing ion-molecule interactions.