Diode laser spectroscopy of ammonia overtone transitions

Diode laser spectroscopy of ammonia ro-vibrational overtone transitions has been performed in the near IR, by using direct absorption, wavelength modulation, and two-tone frequency modulation techniques. Pressure broadening coefficients in air, hydrogen, helium and self-broadening have been measured. The high sensitivity of the apparatus permitted the detection of 70 p.p.m, of NH3 in air per meter of path at atmospheric pressure. New lines have been observed in the 789.3 nm band.