精密分子光谱方法测定波尔兹曼常数

项目名称： 精密分子光谱方法测定波尔兹曼常数

项目编号： No.91436209

项目类型： 重大研究计划

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 胡水明

作者单位： 中国科学技术大学

项目金额： 400万元

中文摘要： 国际计量委员会将基于基本物理常数重新定义开尔文等基本单位，玻尔兹曼常数kB是其中之一。国际科技数据委员会（CODATA）最新kB推荐值的标准相对不确定度0.91ppm，其中绝大部分权重来自于声学共鸣法测量结果。由于单一方法可能带来系统性偏差，目前迫切需要原理完全不同的实验方法来测定kB。通过分子跃迁谱线的多普勒展宽来测量kB，是一种新的全光学测量方案。但是直接吸收光谱方法存在灵敏度不足、测量非线性等限制，很难达到ppm精度。根据我们的分析和前期工作，我们提出，基于我们自己所发展的激光锁频的光腔衰荡光谱方法，结合1mK级的精密温控技术，通过测量分子近红外振转吸收谱线，可实现ppm级精度的光谱跃迁线形测量。我们计划将kB测定至7ppm以下，从而有望进入CODATA，并影响开尔文的新定义。该方法还可被应用于分子精密光谱测量，以及作为新型热力学温度基准方法的研究。

中文关键词： 波尔兹曼常数；光腔衰荡光谱；精密光谱

英文摘要： The International Committee for Weights and Measures adopted a recommendation on redefining the base units like Kelvin using fundamental constants including the Boltzmann constant kB. The kB value recommended by the Committee on Data for Science and Technology (CODATA) has a standard relative uncertainty of 0.91ppm, with an overwhelming contribution from the acoustic gas thermometry method. Since a single method can probably bring a systematic deviation, there is an urgent need of independent determination of kB through a totally different approach. The Doppler Broadening Thermometry is a new rising method for this purpose. But the direct absorption spectroscopy can hardly achieve an accuracy of ppm level, due to insufficient sensitivity and nonlinearity effects. Based on our previous related studies, we propose, using the laser-locked cavity ring-down spectroscopy combined with a temperature-stabilizing system of 1mK precision, and we will be able to measure the profile of a molecular ro-vibrational transition in the infrared with an accuracy of a few ppm. It will allow us to determine the Boltzmann constant with a precision better than 7 ppm, which could be probably included in CODATA and the new definition of Kelvin. The method can also be applied in precision spectroscopy of molecules, and exploring a new standard of thermodynamic temperatures.

英文关键词： Boltzmann constant;Cavity ring-down spectroscopy;Precision spectroscopy