Near-infrared absorption spectroscopy of oxygen and nitrogen gas mixtures

Near-infrared absorption cross-sections of oxygen and nitrogen gas mixtures have been determined from laboratory measurements using Fourier transform spectroscopy and a long path-length absorption cell. Spectra were recorded at instrument resolutions of 0.5 and 0.05 cm−1, between 2 200 and 12 500 cm−1 (4.5–0.8 μm). Cross-sections were determined for mixtures of 21%, 50%, and 75% oxygen in nitrogen, at a total pressure of 100 kPa and temperatures of 200, 230, and 294 K. The absorption `continuaʹ centred at 1.06 and 1.27 μm could each be fitted with two overlapping Voigt profiles: one linearly dependent on oxygen partial pressure, and the other varying quadratically with oxygen partial pressure.