多次反射与加压增强气体拉曼信号方法的研究

Raman Signal Enhancement for Gas Detection Using Multiple Reflections and Increased Pressure

由于气体拉曼散射信号十分微弱,对激光拉曼技术在气体检测领域的应用产生一定的限制,提出一种采用多次反射与增大气体压力合二为一的方式增强气体拉曼散射信号的方法。以常压下空气做为待测成分,在多次反射基础上,采用加压泵将常温、常压下空气压缩到密闭样品池内,保持样品池内压力分别为0.1 MPa、0.2 MPa、0.3 MPa、…、1 MPa等10个不同压力,积分时间1 s条件下,采集空气中O_(2)(特征峰波数位置1552 cm^(-1))、N_(2)(特征峰波数位置2333 cm^(-1))、CO_(2)(特征峰波数位置1278 cm^(-1)、1386 cm^(-1))的拉曼光谱数据,从峰强度、峰面积、信噪比、半峰全宽等4个角度分析特征峰随压力变化情况。发现信噪比与压力呈正相关,基本符合对数关系,压力从0.1 MPa增大到1 MPa,信噪比提升约21 dB。峰强度、峰面积与压力呈正相关,符合线性关系。压力在1 MPa内,特征峰中心位置几乎与压力不相关,半峰宽随压力的变化很小,对比1 MPa与0.1 MPa的数据发现,O_(2)特征峰展宽约为0.7 cm^(-1)。因此,增大气体压力是一种简单有效的增强气体拉曼散射光谱信号的方法,可以在多次反射基础上进一步增强拉曼信号。

Because the gas Raman scattering signal is very weak,the application of laser Raman technology in gas detection is limited.This study presents a method for enhancing the Raman signal for gas detection using multiple reflections and increased pressure.The air under normal pressure is used as the component to be measured,and the air under normal temperature and pressure is compressed into a closed sample tank by a pressure pump.The pressure in the sample tank is maintained at0.1 MPa,0.2 MPa,0.3 MPa,…,1 MPa.The Raman spectral data of oxygen,nitrogen,and carbon dioxide in air (with wave numbers of characteristic peaks at 1552 cm^(-1),2333 cm^(-1),and 1278 cm^(-1)/1386 cm^(-1),respectively) are collected under the conditions of 10 different pressures and an integration time of 1 s.Variations in the characteristic peak with pressure are analyzed according to the four parameters of peak intensity,peak area,signal-to-noise ratio,and half-peak width.Results show that the signal-to-noise ratio is positively correlated with the pressure,which basically conforms to the logarithmic relationship.The signal-to-noise ratio increases by approximately 21 dB when the pressure increases from 0.1 MPa to 1 MPa.The peak intensity and peak area are positively correlated with the pressure and conform to the linear relationship.The central position of the characteristic peak is practically unrelated to the pressure,and the half-peak width changes little with pressure.Compared with the data of 1 MPa and 0.1 MPa,results also show that the oxygen characteristic peak expands to approximately 0.7 cm^(-1).Therefore,increasing the gas pressure is a simple and effective means of enhancing the Raman signal.The Raman signal can be further enhanced based on multiple reflections.