为了研究气压及缓冲气体种类对光声信号及共振频率的影响, 采用光声光谱技术, 设计了一套基于光声光谱技术原理的痕量气体检测系统。实验中以NH3标准气作为待测气体, 采用向光声池内充入缓冲气体的方法来改变光声池内气压, 在气压作为单一变量的条件下得出0.03MPa~0.1MPa气压范围内光声信号及共振频率的变化; 采用分别向光声池内充入不同种类缓冲气体的方法, 得出不同缓冲气体条件下0.03MPa~0.1MPa气压范围内光声信号及共振频率的变化。结果表明, 随着气压的升高, 光声信号幅值增大, 并且越重的缓冲气体使光声信号增幅越大; 气压的升高使得共振频率偏移, 共振频率的偏移量与光声池内混合气体分子的摩尔质量成反比。该研究为解决在现场进行气体检测时, 气压及背景气体变化的复杂环境对检测结果的影响提供了参考。

In order to study effect of pressure and buffer gas on photoacoustic signal and resonance frequency, a trace gas detection system was designed based on photoacoustic spectroscopy. Taking NH3 standard gas as an example, filling buffer gas into the photoacoustic cell to change the pressure in the photoacoustic cell, with the pressure as a single variable, the change of photoacoustic signal and resonance frequency was obtained in pressure range from 0.03MPa ~0.1MPa. And then, different kinds of buffer gases were filled into the photoacoustic cell respectively. The change of photoacoustic signal and resonance frequency in pressure range from 0.03MPa ~ 0.1MPa were obtained under different buffer gas conditions. The results show that, with the increase of pressure, the amplitude of photoacoustic signal increases. The heavier the buffer gas, the greater the increase of photoacoustic signal. The increase of pressure makes the resonance frequency shift. The shift of resonance frequency is inversely proportional to molar mass of the mixed gas molecules in the photoacoustic cell. The change of pressure and background gas makes the environment more complex and affects the detection results. This study provides a reference for solving this problem.