高精密光腔衰荡光谱研究分子碰撞诱导吸收

Precision collision-induced absorption (CIA) of some molecules, are particularly important in the studies to accurately quantify the concentration of carbon dioxide in the Earth's atmosphere, to determine the composition and age of some stars, and to test the CIA theoretical models. An effective way to approach high-accuracy in CIA is to precisely determine the line profiles with experimental methods of very high signal-noise-ratio. The main goal of the present project is as following: Cavity ring-down spectroscopy at various temperatures of high-sensitivity and high-precision will be developed. Combined with a temperature-control system with a precision of 50mK, measurements of line profiles with 10-5 precision will be realized. The line profile parameters with the uncertainty smaller than 0.5 MHz will be established. Precision CIA will be derived by accurately calculate the absorption of active molecule, the weak line-mixing effects and far wing contributions in the whole region. The obtained results will provide a direct examination of the line profile and CIA theoretical model, as well as be used in the astrophysical research.

一些分子的高精度碰撞诱导吸收值，在地球大气二氧化碳浓度精确定量、恒星成分和年龄确定以及碰撞诱导吸收理论模型的检验等方面，具有重要的意义。利用高信噪比的测量手段，准确测量分子光谱线形是获得高精度碰撞诱导吸收值的有效手段。本项目计划发展高灵敏、高精密的光腔衰荡变温探测技术方法，并结合50mK级的精密控温技术，实现10-5精度的分子光谱谱线线形测量；将分子的谱线线形参数测定至0.5 MHz以下,精确计算单体分子跃迁吸收、谱线混合效应和远翼吸收对分子吸收光谱的贡献，获得高精度的分子碰撞诱导吸收实验值，检验光谱谱线线形和碰撞诱导吸收理论模型，以及应用于天体物理的研究。

本项目通过发展高灵敏、高精密的光腔衰荡变温光谱探测技术方法，对重要大气分子吸收光谱进行精密测量，开展分子谱线线形和碰撞诱导吸收方面的研究。取得的主要进展包括：发展了220K - 320K的自锁频激光光腔衰荡变温光谱探测方法，实现了20GHz范围的光谱扫描，探测灵敏度进入了10^-13/cm 水平；利用该系统研究了重要大气分子的高精密光谱，统计误差10-5水平，获得了N2-N2体系在近红外的碰撞诱导吸收实验数据；利用所建立的实验装置，测量了CO2和CO分子在重要大气窗口的近红外振转谱线的饱和吸收光谱，将频率不确定度提高至kHz水平，并提出可基于近红外振转光谱研究双原子分子在Born-Oppenheimer 近似高阶修正下的Dunham模型是否正确。