Near-Infrared Molecular Emission from a Gas Fountain

Abstract

An electrothermal fountain is used to heat gas-phase samples in the range of 300 to 400°C in order to observe their near-infrared (NIR) emissions. In conjunction with the fountain, a 1/8-m Ebert monochromator and an uncooled PbS detector are shown to be sufficiently sensitive for recording the NIR fingerprints of CH4, CO2, N2O, and C2H6. At fountain temperatures of approximately 400°C, the molecular emission is confined to the long wavelength NIR region (1600–2500 nm) and yields limits of detection in the range of 4 to 10% v/v (3–10 mg/s). Reproducibilities have relative standard deviations of 3.0%. The calibration curves for the gases examined in this study have small linear dynamic ranges (factors of 2 to 10) and exhibit some degree of upward curvature. Ramifications of the application of NIR molecular emission spectroscopy to the qualitative and quantitative analyses of mixtures are discussed.