An intense slit discharge source of jet-cooled molecular ions and radicals (Trot < 30 K

A novel pulsed, slit supersonic discharge source is described for generating intense jet-cooled densities of radicals (> 1012 / cm3) and molecular ions (> 1010 / cm3) under long absorption path (80 cm), supersonically cooled conditions. The design confines the discharge region upstream of th supersonic expansion orifice to achieve efficient rotational cooling down to 30 K or less. The collisionally collimated velocity distribution inn the slit discharge geometry yields sub-Doppler spectral linewidths, which for open-shell radicals reveals spin-rotation, splittings and broadening due to nuclear hyperfine structure. Application of the slit source for high-resolution, direct IR laser absorption spectroscopy in discharges is demonstrated on species such as OH, H3O+ and N2H+.