Method and apparatus for the detection of a gas using photoacoustic spectroscopy
First Claim
1. A method for the detection of a first gas in a gas mixture through photoacoustic spectroscopy, wherein the gas mixture further comprises a second gas the absorption spectrum of which interferes with the absorption spectrum of the first gas, wherein the gas mixture is irradiated by pulsating laser light having a constant pulsation frequency and therefore a uniform wavelength during the measurement and wherein the wavelength of the laser light is varied gradually and wherein the measurement comprises at least one reading of the phase of the photoacoustic signal as a function of the uniform wavelength during measurement, characterized in that a photoacoustic measurement is carried out in the presence of a third gas in the gas mixture, said third gas being present in the gas mixture or being added to the mixture immediately before the measurement and exhibiting kinetic cooling in combination with the first or the second gas.
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Abstract
In a process for the detection of a first gas in a gas mixture comprising a second gas, the absorption spectre of which interferes with the absorption spectre of the first gas, a photoacoustic measurement is carried out in the presence of a third gas which in combination with the first or the second gas exhibits kinetic cooling. During measurement the gas mixture is influenced by pulsating laser light having a constant repetition frequency where the frequency of the laser light is varied gradually. The measurement comprises at least one detection of the phase of the photoacoustic signal as a function of the laser light frequency. The invention further relates to an apparatus for carrying out the invention.
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Citations
9 Claims
- 1. A method for the detection of a first gas in a gas mixture through photoacoustic spectroscopy, wherein the gas mixture further comprises a second gas the absorption spectrum of which interferes with the absorption spectrum of the first gas, wherein the gas mixture is irradiated by pulsating laser light having a constant pulsation frequency and therefore a uniform wavelength during the measurement and wherein the wavelength of the laser light is varied gradually and wherein the measurement comprises at least one reading of the phase of the photoacoustic signal as a function of the uniform wavelength during measurement, characterized in that a photoacoustic measurement is carried out in the presence of a third gas in the gas mixture, said third gas being present in the gas mixture or being added to the mixture immediately before the measurement and exhibiting kinetic cooling in combination with the first or the second gas.
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