Line strength and collisional broadening studies of hydrogen sulphide in the 1.58 mu m region using diode laser spectroscopy

High resolution diode laser spectroscopy has been applied to the detection of hydrogen sulphide at ppm levels utilizing different transitions within the region of the ν 1+ν 2+ν 3 and 2ν 1+ν 2 combination bands around 1.58 μm. Suitable lines in this spectral region have been identified, and absolute absorption cross sections have been determined through single-pass absorption spectroscopy and confirmed in the Doppler linewidth regime using cavity enhanced absorption spectroscopy (CEAS). The desire for a sensitive system potentially applicable to H2S sensing at atmospheric pressure has led to an investigation on suitable transitions using wavelength modulation spectroscopy (WMS). The set-up sensitivity has been calculated as 1.73×10-8 cm -1∈s1/2, and probing the strongest line at 1576.29 nm a minimum detectable concentration of 700 ppb under atmospheric conditions has been achieved. Furthermore, pressure broadening coefficients for a variety of buffer gasses have been measured and correlated to the intermolecular potentials governing the collision process; the H2S-H2S dimer well depth is estimated to be 7.06±0.09 kJ∈mol-1. © 2008 Springer-Verlag