Pulsed discharge source of supersonically cooled transient species

A source combining dc discharge with pulsed supersonic expansion is shown to be a versatile tool for spectroscopic studies of a variety of transient species. High concentrations of cold small radicals have been generated using suitable precursors, and detected by laser induced fluorescence. Discharging of halogenated methanes provides an efficient source of halogenated carbenes. Molecular radical cations are similarly efficiently produced, probably as a result of the Penning ionization process in collisions with metastable rare-gas atoms. Reactive sputtering of electrodes is shown to result in the production of metal halides and similar simple metal compounds. An application of the discharge source as a useful tool for matrix isolation studies is proposed and discussed.