Cavity ring down spectroscopy on radicals in a supersonic slit nozzle discharge

Abstract

A sensitive and generally applicable technique for direct absorption spectroscopy on electronic transitions of transient species in the gas phase is presented. The method is based on cavity ring down spectroscopy in a pulsed slit nozzle, incorporating a discharge in a high pressure supersonic expansion. The performance is demonstrated with spectra of the 000 origin band of the Π2←X2Π electronic transition of the isoelectronic linear carbon chain radicals C6H and C6H2+. Rotationally resolved and rotationally cold spectra (Trot<15 K) have been obtained. The sensitivity of the technique is demonstrated for anions with a detection limit as low as 107 C2− molecules cm−3 for rovibrational transitions of the B2Σu+←X2Σg+ system.