2001 Volume 17 Issue 12 Pages 1441-1443
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 μm (1087 cm-1) and 10.7 μm (935 cm-1) at a constant 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.