A detailed understanding of many photochemical processes in the troposphere requires simultaneous measurements of the abundances of oxidants and the oxides of nitrogen. The goal of this research is to develop capabilities for nearly simultaneous measurements of key oxygen containing free radicals and oxides of nitrogen in the atmosphere with high specificity and sensitivity using a spectroscopic technique. Ambient samples are drawn through nozzles into two separate detection chambers -- one for OH/HO2, pumped to 0.01 atmosphere; one for NO2/NO, pumped to (0.01-1) atmosphere -- where the radicals are detected by laser induced fluorescence. A high repetition rate (10 kHz) copper vapor laser pumps two dye lasers -- one frequency doubled to the 282 nm or 309 nm transitions of OH, the other operated at the 585 nm transitions of NO2. Resonantly scattered photons are detected by high efficiency optics and photomultiplier tubes and are distinguished from background signals by tuning the dye lasers on and off molecular resonances. HO2 and NO are detected by chemical conversion with NO and O3 to OH and NO2 respectively. The estimated detection limit (S/N ratio - 2) for OH/HO2 is .005 pptv (1.3 x 107 cm-3) in ten seconds. This detection system will be used primarily for ground-based field measurements, but also in some requisite laboratory photochemical studies, and as a development tool for detection with other light sources and for other species.
|Effective start/end date
|4/15/90 → 9/30/93
- National Science Foundation: $371,321.00