INFRARED-ABSORPTION SPECTROSCOPY OF MOLECULAR-IONS IN A CORONA-DISCHARGE SLIT EXPANSION

A new corona slit nozzle has been constructed to study, by means of direct infrared absorption, molecular ions generated in a continuous supersonic expansion. Spectra of the ions H-3(+), D2H+, D-3(+), HN2+, H3O+ and ArH+, were detected in the 1900-3600 cm(-1) region using difference frequency and diode laser sources. The new jet source gives a significant improvement in signal-to-noise ratio and a reduction in rotational temperature compared to our previously reported hollow-cathode jet discharge source. The effective rotational and translational temperatures were in the ranges 33-93 and 50-100 K, respectively. The experimental factors influencing the performance of the source are discussed.