石英晶振用于石英增强光声光谱系统的优化实验研究

研究了音叉式石英晶振的个体尺寸、安放角度、探测部位以及外部污染对整个石英增强光声光谱系统(QEPAS)的探测灵敏度影响。测试了国内外十种不同音，结果表明顶端为楔形构造的音叉式石英晶振比规则的长方体构造的音叉拥有更高的品质因数(Q值)。在相同的测试条件下探测水的吸收线(7 306 cm-1)时获得更高的灵敏度，探测信号的强度相差高达50%。在研究音叉安放角度对探测信号影响的实验中，发现音叉的旋转角度与俯仰角度对探测信号的强度几乎没有影响，但是当光束以角度φ斜入射时，更多的噪声被带入到测量中。在正入射的情况下音叉的最佳响应位置在距离音叉底部约3.1 mm。定性研究了外部杂物污染对音叉频率的影响，发现随着污染物的附着，石英音叉的频率会呈现降低的趋势，提供了一种改变音叉式石英晶振的共振频率的方法，为石英音叉用于较低调制频率的探测提供了一种理论可能，这对于石英增强光声光谱技术用于V-T弛豫率较慢的痕量气体检测有重要的意义。

Experimental Research on Optimization of QEPAS Based Spectrophone

The present paper studied the impact of geometry dimensions, located angle and detection position of a quartz tuning fork (QTF) on the sensitivity of QEPAS system. Ten kinds of QTFs were employed to compare the sensitivity with each other, and the results show that the QTF with a wedge-shape top obtains a higher quality factor and turns to be 50% more sensitive than the ones with a regular cuboid top when detecting the water concentration at 7 306 cm-1. By studying the located angle of a QTF, it was found that it nearly makes no difference, but more noise is introduced when there is an angle φ between the laser beam and QTF. The optimal detection position of a QTF appears to be 3.1 cm away from the bottom of the QTF under the case of the normal incidence. At last the influence of external contamination on the resonant frequency of a QTF is discussed. The authors found that the frequency of the QTF decreases along with the contamination increasing. A novel method to lower the frequency of the QTF is proposed. This may make a contribution to the QEPAS used in detecting trace gas with a low V-T relaxation.