Water vapour and carbon dioxide interference in the high sensitivity detection of NH3 with semiconductor diode lasers at 1.5 μm

Abstract H 2 O and CO 2 interferences with NH 3 absorption lines in the combination band at 1.5 μm are investigated by means of diode laser spectroscopy, in conjunction with a high sensitivity two-tone frequency modulation technique. Two different spectral regions 6685–6700 cm −1 and 6475–6494 cm −1 , respectively are analyzed, and the strongest interference free ammonia lines are identified as possible candidates for high sensitivity detection of ammonia traces in air. Detection limits of 4.5 ppm m at 6482.69 cm −1 and 4 ppm m at 6689.56 cm −1 for ammonia in air at atmospheric pressure are demonstrated. In addition, self and air broadening parameters are measured for some of the investigated lines.