Patent ID: 6202470
Filing Date: 2001-03-20
Classification: G01N

Abstract:
A method for photoacoustic detection of a suspected constituent in a vapor sample disposed in open air having an associated noise level in an effluent containing a mixture of constituents, the suspected constituent having at least one absorption wavelength in the range of approximately 1700 to 2500 nm, the method comprising:providing the effluent containing the mixture of constituents in open air;directing electromagnetic radiation into the effluent vapor sample, the radiation tunable to selected wavelengths between 1700 to 2500 nm, to correspond to at least one absorption wavelength of the suspected constituent and having sufficient energy to generate acoustical waves having a level above said noise level in the vapor sample in response to said absorption, said electromagnetic radiation generated from a pulsed laser source having a pulsed laser wavelength and being selected from the group consisting of a pulsed Co:MgF.sub.2 laser, a pulsed diode laser, and a pulsed optical parametric oscillator laser;detecting the acoustical waves generated in response to absorption and producing an electronic signal proportional to the intensity of the acoustic wave; andidentifying the effluent from the characteristics of the acoustic signal as functions of the pulsed laser wavelength.