氢分子近红外振转光谱的精密测量

Molecular hydrogen is the most fundamental, and the only neutral molecule expected to be both calculated and measured with extremely high accuracy. High-precision measurements of its spectroscopy, espectially the levels at the electric ground state, play an important role in the examination of precise quantum chemistry calculations and some fundanmental physical constants. In the infrared region, H2, being a homonuclear diatomic molecule, has no rotation-vibrational dipole transitions . Only very weak electric quadrupole transitions are allowed. In this project, we plan to establish a new spectroscopy approach with ultra-high precision and sensitivity, based on a laser-locked cavity ring-down spectrometer.An equivalent absorption path-length of thousands of kilometers and a frequency precision of 10-5cm-1 are expected. Precision infrared ro-vibrational spectroscopy of the molecular hydrogen will be measured.The obtained results will provide a direct examination of the high-accuracy quantum theory taking into account the the high-level QED and relativistic corrections.The possibility to determine some fundamental physical constants including the electron/proton mass ratio in amolecular system will be discussed.

氢分子是最基本的分子，也是目前唯一的在理论和和实验上都有望达到极高精度的中性分子。高精密的氢分子光谱，特别是其电子基态的能级结构，可以检验高精度量子化学计算方法甚至基本物理常数。作为同核双原子分子，氢分子不存在电偶极红外振转跃迁，仅有极微弱的电四极矩跃迁。本项目计划利用高灵敏的光腔衰荡光谱技术，结合激光精密稳频技术，实现等效吸收光程达数千千米、光谱测量精度好于10-5cm-1的光腔衰荡光谱探测，对氢分子近红外泛频振转光谱进行高精密测量，对包含相对论和高阶量子电动力学修正的高精度量子化学理论进行直接的检验，并探讨在该分子体系中实现对电子/质子之比等基本物理常数进行测定。

氢分子是自然界最简单的中性分子，也是目前唯一的在理论计算和和实验上都有望达到极高精度的分子。高精密的氢分子光谱，特别是其电子基态的能级结构，可以检验高精度量子化学计算方法，以及基本物理常数数值。作为同核双原子分子，氢分子不存在电偶极红外振转跃迁，仅有极微弱的电四极矩跃迁。本项目旨在利用高灵敏的光腔衰荡光谱技术，结合激光精密稳频技术，实现等效吸收光程达数千千米、光谱测量精度好于10-5cm-1的光腔衰荡光谱探测，对氢分子近红外泛频振转光谱进行高精密测量。本项目于2014年开展工作，基于近红外钛宝石激光源，利用温度控制的宽带超稳腔F-P标准具作频率参考和激光频率锁定，借助铷等原子跃迁吸收作绝对频率基准，并结合高灵敏的光腔衰荡光谱技术，建立了检测灵敏度达到10-11/cm水平、绝对频率精度10-5cm-1的高精密光谱测量方法。利用该方法，测量了氢分子750-850nm波段振-转光谱第二泛频带（3-0），共观测到八条谱线，其中六条谱线的绝对频率精度达到3X10-4cm-1，好于理论计算结果，而最弱的S(4)和S(5)跃迁线，属于实验上首次观测到的谱线。八条谱线的谱线强度测量结果与理论计算结果相一致，也很好地验证了量子化学计算结果，并为天文学研究提供有力的数据支持。