Background signal in a photoacoustic system

摘要

In order to investigate the sources of the background signal in a photoacoustic system, the wavelength dependence of background signal has been measured in Ar and C_2H_2 gas, respectively. When Ar was used as sound carrier, the background photoacoustic signal arises from optical heating of the reflecting mirrors, that is the mirror noise. When polyatomic gas, such as C_2H_2, was filled in the photoacoustic cell, the background signal is due to photoacoustic Raman effect in addition to the noise produced at the reflecting mirrors. In near-infrared and visible region, the photoacoustic Raman signal is of the same order of magnitude as mirror noise.