利用CRASY光谱鉴别并定量分析分子空间异构体及其光解立体动力学

分子空间异构体，即立体异构体，在反应活性和立体动力学机理上有很大差异，传统光谱学方法很难对分子的立体异构体进行鉴别和分析。本项目拟利用质量相关转动准直光谱（CRASY）,实现分子中空间异构体组分的鉴别和定量分析。该技术，首先用一束皮秒激光激发分子的相干转动态；然后用另一束飞秒激光对相干转动态进行电离探测，当分子沿空间某一方向准直时电离几率最大。调节两束光之间的延迟，获得调制的质谱信号，经傅立叶变换转化成频谱信息，即转动光谱。立体异构体由于空间结构的差异，表现出的转动光谱不同。利用CRASY光谱实现异构体组分的鉴别和定量分析，具有很高的灵敏度。本项目拟进一步将该方法应用到具有空间异构组分的分子体系的光解立体动力学研究中。该研究有助于我们深入理解自然界物质存在的内在分子本质，建立分子外在功能与内部微观结构的联系，推动分子立体动力学研究以及利用转动光谱开展快速化学分析的发展与进步。

Stereoisomers,which are difficult to identified and analyzed with traditional spectroscopy, show different reactivity and Stereodynamics in reation. Here, we present a mass-correlated rotational alignment spectroscopy (CRASY) to identify and quantitatively analyze the naturally accurring stereoisomers in molecular samples. In this mass-CRASY method,the molecules are excited by an initial short picosecond laser pulse to the coherent rotational states. A second laser pulse ionizes the molecules. The largest ionization probability occurs during the time interval when the molecules are aligned in one spatial direction.Varying the delay time between two laser pulses will produce a series of peaks and valleys in the signal over time. The time-delay data can be converted into frequency spectra with Fourier transform, i.e. the rotational spectra. The spacial structure differences between stereoisomers result in unique rotational spectroscopy.This method can realized the identification and quantitative analysis of stereoisomers providing high detection sensitivity. It will also be carried into the study of photodissociation stereodynamics in molecules having stereoisomers further. This project will help us to understand the molecular essence of objects in nature and to build the bridge from interior microstructure to external function of molecules. Also, this will pave the way for the stereodynamics in molecular reaction and "sample-in, structure-out" chemical analysis.