Measurement of nitric oxide with an antimonide diode laser

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Abstract
An antimonide diode laser operating near 2.65 µm was used to measure absorption lines of NO gas in the first overtone band. A blended line pair of NO that is sufficiently free of interference from H2O to permit the selective detection of NO under reduced pressure conditions was identified. With wavelength-modulation spectroscopy, a rms noise level equivalent to an absorbance of 3.2 × 10-5 was achieved at a measurement integration time (for a single spectral data point) of 0.1 s. The corresponding detection sensitivity (signal-to-noise ratio of 2) for NO in air at reduced pressure was ∼15 ppm m (ppm is parts in 106). Antimonide diode lasers show substantial promise for gas-sensing applications because they can gain access to relatively strong absorption lines of several gases of environmental interest at operating wavelengths at which cryogenic cooling is not required.