LASER ABSORPTION METHANE ISOTOPE ANALYZER

ANALYSIS OF THE STABLE ISOTOPES IN ATMOSPHERIC METHANE SAMPLES CAN BE USED TO IDENTIFY LOCAL SOURCES AND TO DEFINE THE GLOBAL BUDGET OF THIS RADIATIVELY IMPORTANT GREENHOUSE GAS. THE PROJECT IS DEVELOPING A PORTABLE AND LESS EXPENSIVE ALTERNATIVE TO ISOTOPE MASS SPECTROMETRY FOR MEASURING (13)CH4 AND CH3D COMPONENTS IN METHANE SAMPLES. THE METHOD IS BASED ON INFRARED ABSORPTION USING A HELIUM NEON LASER AT 2999.24 CM(-1). THE LASER LINE CAN BE ZEEMAN SHIFTED INTO COINCIDENCE WITH CLOSELY SPACED LINE PAIRS OF (13)CH4 - (12)CH4 AND CH3D - CH4 SO THAT BOTH RATIOS MAY BE OBTAINED WITH A SINGLE INSTRUMENT AND SAMPLE. RESEARCH IDENTIFIES THE EXACT LINE POSITIONS OF THESE PAIRS AND THE LASER LINE USING TUNABLE DIODE LASER SPECTROSCOPY, AND ESTABLISHES THE BASELINE PARAMETERS FOR EVALUATING THE ULTIMATE SENSITIVITY OF THE TECHNIQUE.