Ion-molecule reactions in the gas phase are very fast, dominant processes. They are important in the understanding of widely differing environments such as discharge plasmas, the ionosphere and interstellar medium. Because of the ephemeral nature of ionic species their structure and properties are rather poorly characterized and there is a need for much more experimental observation in this area. Spectroscopic work over the last ten years has produced a rapid development of our knowledge of molecular ions, mostly through laser sampling of extended glow discharges. The present proposal falls in this area. A new microwave discharge source for the generation of transient species has recently been developed. We propose to modify this source so that it can be used in the mid-infrared region. A carbon monoxide laser magnetic resonance spectrometer, working in the frequency region 1250-2080 and 2500-3500 cm-1, is already in existence in Dr. Brown's laboratorv in Oxford. We would aim to detect the bending fundamental band of H2O at 1408 cm-1 as a proving experiment. After that, we would search for new species such as HO2+ and CH2+ about which essentially nothing is known.