LASER ABSORPTOMETER FOR DETECTION OF TRACE SPECIES

WITH THE INCREASE IN ATMOSPHERIC POLLUTION AND A NEW, GROWING PUBLIC AWARENESS OF RESULTING ENVIRONMENTAL DAMAGE, THERE IS A NEED FOR NEW TECHNOLOGY TO MEASURE THE CONCENTRATION OF TRACE SPECIES IN THE ATMOSPHERE. EXTRACTIVE METHODS, IN WHICH A SEALED SAMPLE OF AIR IS ANALYZED IN A LABORATORY, ARE EXPENSIVE AND ARE INAPPLICABLETO CONTINUOUS, IN SITU MONITORING OF CONCENTRATIONS. SCIENCE RESEARCH LABORATORY PROPOSES THE DEVELOPMENT OF AN INSTRUMENT CALLED A LASER INTERFEROMETRIC ABSORPTOMETER (LIA) TO FILL THIS NEED. THE BASIS OF THIS INSTRUMENT IS THE INTERFEROMETRIC MEASUREMENT OF THE OPTICAL-PATH CHANGE THAT OCCURS IMMEDIATELY AFTER A PULSED LASER BEAM IS ABSORBED BY TRACE SPECIES PRESENT IN ONE ARM OF THE INTERFEROMETER. THE LIA WILL BE SENSITIVE TO PARTS-PER-TRILLION TRACE-GAS CONCENTRATIONS, 2-3 ORDERS OF MAGNITUDE BETTER THAN INSTRUMENTS BASED ON OTHER APPROACHES TO MONITOR TRACE SPECIES IN THE FIELD.