Remote sensing by differential optical absorption spectroscopy and diode laser spectroscopy
- Unisearch Associates Inc., Concord, Ontario (Canada)
Differential Optical Absorption Spectrometry (DOAS) is based on the absorption of visible and ultraviolet radiation. A number of important pollutants, including the criteria gases O{sub 3}, NO{sub x} and SO{sub 2} absorb radiation in this portion of the spectrum.. The method is not as universal as FTIR but can measure certain gases such as the benzene, toluene, and xylene, which cannot be readily measured by FTIR because of interferences from ubiquitous CO{sub 2} and H{sub 2}O. The sensitivity and resolution of DOAS are generally suitable for most applications. DOAS instruments are rugged and relatively uncomplicated requiring little skill and training to operate. The greatest complexity is in the data analysis which requires relatively sophisticated software Near infrared, Tunable Diode Laser Spectroscopy (TDLAS) is based on absorption of near-infrared radiation. The light sources are laser diodes of the type used in optical fiber communications and in consumer products such as CD players and laser printers. Modulation of this light source provide the required spectral information. The detector end of light path requires no spectrometer or complex analytical software. Although not as universal as either FTIR and DOAS, TDLAS systems have the highest spectral resolution of any method available and therefore provides measurements of specific gases which are free of interferences from other gases. It is also capable of high sensitivity and time response. Another major advantage is that fiber optics can be used to make measurements at a number of remote locations simultaneously with a single instruments. The main limitation to the method is that a separate diode laser must generally be used for each gas. But since these diode lasers are quite small a number of them can be placed within the same instrument and multiplexed to measure a number of selected gases simultaneously.
- OSTI ID:
- 351225
- Report Number(s):
- CONF-970677-; TRN: IM9926%%27
- Resource Relation:
- Conference: 90. annual meeting and exhibition of the Air and Waste Management Association, Toronto (Canada), 8-13 Jun 1997; Other Information: PBD: 1997; Related Information: Is Part Of 1997 proceedings of the Air and Waste Management Association`s 90. annual meeting and exhibition; PB: [7000] p.
- Country of Publication:
- United States
- Language:
- English
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