Diode laser based detection and determination of pressure-induced broadening coefficients in the v_1 + v_3 combination band of ammonia

摘要

Nitrogen, oxygen, air and self-broadening coefficients have been measured in direct absorption for six transitions in the v_1 + v_3 combination band of ammonia at room temperature using a DFB diode laser operating at 1.51μm. Absorption cross-sections for these strong lines, suitable for detection purposes, have been determined. Using 2f wavelength modulation spectroscopy we demonstrate a minimum detectable concentration of 500 ppb in a 75 cm path in 1 s at atmospheric pressure and present a simple method for measurement of broadening coefficients.