AN INTENSE SLIT DISCHARGE SOURCE OF JET-COOLED MOLECULAR-IONS AND RADICALS (T-ROT-LESS-THAN-30K)

A novel pulsed, slit supersonic discharge source is described for gene rating intense jet-cooled densities of radicals (> 10(12)/cm(3)) and m olecular ions (> 10(10)/cm(3)) under long absorption path (80 cm), sup ersonically cooled conditions. The design confines the discharge regio n upstream of the supersonic expansion orifice to achieve efficient ro tational cooling down to 30 K or less. The collisionally collimated ve locity distribution in the slit discharge geometry yields sub-Doppler spectral linewidths, which for open-shell radicals reveals spin-rotati on splittings and broadening due to nuclear hyperfine structure. Appli cation of the slit source for high-resolution, direct IR laser absorpt ion spectroscopy in discharges is demonstrated on species such as OH, H3O+ and N2H+.