Diode-laser absorption measurements of CO2, H2O, N2O, and NH3 near 2.0 μm
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, H2O, N2O, and NH3 concentrations in various flowfields using absorption spectroscopy and extractive sampling techniques. An external-cavity diode laser with a tuning range of 1.953–2.057 μm was used to record absorption lineshapes from measured transitions in the CO2 4ν20+ν3, ν1+2ν20+ν3, and 2ν1+ν3 bands, H2O ν2+ν3and ν1+ν2 bands, N2O 2ν1+4ν20, ν21+2ν3, 3ν1+2ν20, and 4ν1 bands, and NH3ν1+ν4 and ν3+ν4 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 lineshape measurements were used to determine fundamental spectroscopic parameters including the line strength, line-center frequency, and self-broadening coefficient of the probed transition. The results represent the first measurements of CO2, H2O, N2O, and NH3 absorption near 2.0 μm using room-temperature near-IR diode lasers.
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