光外差-磁旋转-浓度调制光谱技术

Optical Heterodyne-Magnetic Rotation-Concentration Modulation Spectroscopic Technique

介绍了一种针对瞬态分子光谱测量的新技术:光外差磁旋转浓度调制光谱技术,这种光谱技术具有很高的灵敏度,综合了光外差探测技术、磁旋转光谱技术和浓度调制光谱技术的特点,利用浓度调制光谱技术针对寿命很短的瞬态分子和激发态分子的光谱进行测量,利用光外差探测技术可以消除来自光源的幅度涨落噪声,实现散粒噪声的测量极限,利用磁旋转光谱技术可以对顺磁性分子进行选择性的测量,并且进一步提高探测灵敏度。详细讨论了这种光谱技术的工作原理,并用这种技术对O2分子的b1Σg+-X3Σg-三重禁戒跃迁光谱进行测量,获得了很好的测量信噪比。并对该技术的灵敏度作了详细的分析,估计最小相对吸收度可达1.9×10-9以及O2分子三重禁戒跃迁的吸收截面为σ=2.4×10-24cm2。

A new spectroscopic technique for measuring the spectrum of transient molecules, named optical heterodyne magnetic rotation enhanced concentration modulation spectroscopy (OH-MR-CMS) is introduced. It combines optical heterodyne detection and magnetic rotation spectroscopy with the concentration modulation technique leading to greatly improved sensitivity. The concentration modulation spectroscopy (CMS) is suitable for the detection of the spectrum of short-lifetime transient molecules and excited state molecules. The optical heterodyne (OH) technique is used for eliminating the amplitude fluctuation noise from the laser source so as to realize the detection limit of the shot noise. The magnetic rotation (MR) technique makes a selective detection of paramagnetic molecules, so as to further improve the detection sensitivity. The principle of OH-MR-CMS is interpreted in detail and the technique is used to measure the absorption spectrum of the O2 b1Σg+ - X3Σg- forbidden transition with a quite good signal-to-noise (S/N) ratio. The detailed analysis of the sensitivity of this technique is presented, the minimum relative absorption is approximately 1.9 × 10-9 and the absorption cross-section σ of the O2 forbidden transition is 2.4 × 10-24 cm2.