Flowing liquid-sheet jet for cavity ring-down absorption measurements

The use of a flowing liquid-sheet jet in cavity ring-down absorption measurements is described. A mechanical gear pump was used to pump solvent at low pressure through a circular orifice. The resulting cylindrical jet of solvent was fired at a flat surface. A flat sheet of liquid was formed in a small portion of the resulting spray, which was sufficiently stable to be positioned at the Brewster angle in a linear ring-down cavity setup operated with a pulsed laser. The path length through a sheet-jet of ethylene glycol was measured to be 23.2 +/- 0.6 mum. Malachite Green dye was used as an analyte to demonstrate a linear dynamic range of 12.6 dB (73.9 nM to 1.34 microM). The limit of detection for the system was determined to be alpha LOD = 0.0162 cm(-1), or 71 nM (at epsilon = 9.975 x 10(4) M(-1) cm(-1), 628 nm, 3 sigma). The technique is shown to have promise for analytical and spectroscopic measurements, for example, in studies of gas-liquid interfaces.