Laser photoacoustic spectroscopy is a laser measurement method with high sensitivity, good selectivity, nondestructive, and fast response (real-time). In the present work, to detect carbonyl sulfide and ethene gases and measure resonant frequencies and signals, the photoacoustic spectroscopy system was designed and set up. The detection limit of this system to trace ethene and carbonyl sulfide was measured 3 ppb and 8 ppb, respectively. Also, for these two gases at the presence of different buffer gases, the resonant frequency and photoacoustic signal were recorded. The results showed that among the used buffer gases, xenon has the best acoustic performance and gives the highest photoacoustic signal. The signal also increased with increasing pressure of buffer gas, because increasing the pressure leads to improved collisional processes. The study of resonant frequencies of this system for these two gases in the presence of buffer gases showed that with increasing the pressure of xenon, argon, and nitrogen buffer gases from 65 to 765 Torr, the resonant frequency does not change significantly. But in the case of helium buffer gas, these resonant frequency changes are significant, and as the helium pressure increases by 65 to 765 Torr, the resonant frequencies of carbonyl sulfide and ethene change from 2016 to 2630 Hz and from 2100 to 2740 Hz, respectively. The reason for the different behavior of helium is the higher speed of sound in helium than in other buffer gases.
