DIODE-LASER ABSORPTION-MEASUREMENTS OF CO2, H2O, N2O, AND NH3 NEAR 2.0 MU-M

A diode-laser sensor has been developed for sensitive measurements of CO2, H2O, N2O, and NH3 concentrations in various flowfields using abso rption spectroscopy and extractive sampling techniques. An external-ca vity diode laser with a tuning range of 1.953-2.057 mu m was used to r ecord absorption lineshapes from measured transitions in the CO2 4 nu( 2)(0) + nu(3), nu(1 +) 2 nu(2)(0) + nu(3), and 2 nu(1) + nu(3) bands, H2O + nu(3) and nu(1) + nu(2) bands, N2O 2 nu(1) + 4(2)(0), nu(2)(1) 2 nu(3), 3 nu(1) + 2 nu(2)(0), and 4 nu(1) bands, and NH3 nu(1) + nu( 4) and nu(1) + nu(4) bands. Measured CO2, H2O, and N2O survey spectra were compared to calculations to verify the HITRAN96 database and used to determine optimum transitions for species detection. Individual li neshape measurements were used to determine fundamental spectroscopic parameters including the line strength, line-center frequency, and sel f-broadening coefficient of the probed transition. The results represe nt the first measurements of CO2, H2O, N2O, and NH3 absorption near 2. 0 mu m using room-temperature near-IR diode lasers.