- Conference date: 17–21 May 2009
- Location: Cairo (Egypt)
A photoacoustic (PA) spectrometer is presented for the sensitive detection of carbon monoxide (CO) using a CO laser operating on 9 lines in the 1→0 vibrational transition. Spectroscopy with gas lasers usually depends on accidental coincidences with the absorption spectrum, but the CO laser operation in the fundamental band yields perfect coincidences and, hence, strong absorption signals. The observed PA spectra of CO in are however, a factor of 10 to small and have an inverted phase. These peculiarities are explained with the near‐resonant energy transfer from vibrationally excited CO molecules to molecules, leading to a (transient) kinetic cooling of the mixtures. The paper gives the first study of this effect in mixtures. Relating the observed signals in the gas mixtures to the observed background and noise figures allows one to derive a detection limit of 20 ppb for CO in with the current setup.
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