Sun Y R, Pan H, Cheng C-F, Liu A-W, Zhang J-T, Hu S-M
Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, China.
Opt Express. 2011 Oct 10;19(21):19993-20002. doi: 10.1364/OE.19.019993.
The Boltzmann constant can be optically determined by measuring the Doppler width of an absorption line of molecules at gas phase. We propose to apply a near infrared cavity ring-down (CRD) spectrometer for this purpose. The superior sensitivity of CRD spectroscopy and the good performance of the near-ir lasers can provide ppm (part-per-million) accuracy which will be competitive to present most accurate result obtained from the speed of sound in argon measurement. The possible influence to the uncertainty of the determined Doppler width from different causes are investigated, which includes the signal-to-noise level, laser frequency stability, detecting nonlinearity, and pressure broadening effect. The analysis shows that the CRD spectroscopy has some remarkable advantages over the direct absorption method proposed before. The design of the experimental setup is presented and the measurement of C2H2 line near 0.8 μm at room temperature has been carried out as a test of the instrument.
玻尔兹曼常数可以通过测量气相中分子吸收线的多普勒宽度来进行光学测定。我们建议为此应用一台近红外腔衰荡（CRD）光谱仪。CRD光谱的卓越灵敏度和近红外激光器的良好性能能够提供百万分之一（ppm）的精度，这将与目前通过氩气声速测量获得的最精确结果相竞争。研究了不同原因对所确定的多普勒宽度不确定性的可能影响，其中包括信噪比水平、激光频率稳定性、检测非线性以及压力展宽效应。分析表明，CRD光谱相对于之前提出的直接吸收法具有一些显著优势。给出了实验装置的设计，并在室温下对0.8μm附近的乙炔谱线进行了测量，作为对该仪器的测试。
