Analytical Sciences

Abstract − Analytical Sciences, 17(12), 1441 (2001).

High-resolution Spectra of Bromo Methane and Methyl Bromide Obtained by a Continuously Tunable 10-bar CO2 Laser Based Photoacoustic Spectrometer
Albert Romann and Markus W. Sigrist
Swiss Federal Institute of Technology (ETH), Institute of Quantum Electronics, Laboratory for Laser Spectroscopy and Environmental Sensing, CH-8093 Zürich, Switzerland
High resolution spectral data of 100 ppmV (10-6 per volume) concentrations of the trace gases bromo methane (BM, CH3Br), and methyl bromide (DME, (CH3)2O), buffered in synthetic air (80% N2, 20% O2) at atmospheric pressure and room temperature are reported. The spectra are recorded with a continuously tunable 10-bar CO2 laser based photoacoustic (PA) spectrometer. The tuning range covers 76 cm-1 between 9.2 um (1087 cm-1) and 10.7 um (935 cm-1) at a constand narrow line-width of 0.018 cm-1 (540 MHz). The non-resonant PA measuring cell employs an in-line 10-microphone array. The estimated detection limits for BM and DME are approximately 2 ppmV for a signal-to-noise ratio (SNR) of 3. This corresponds to a calculated detection limit of  ~76 ppbV for ethylene.