线性分子摆动光谱Q支相对强度与电场、分子取向度的依赖关系及其应用

Dependence of Q-Branch Intensity of Pendular State Molecules on Electric Field and Molecular Orientation and Their Applications

提出了一种测量分子取向度的新方法,即采用极性线性分子的摆动光谱Q支相对强度来测量分子的取向度。通过计算极性分子HCN-N2电子基态的C—H伸缩振动在不同电场强度下的摆动光谱,发现其摆动光谱的Q支强度随着电场强度的增大而逐渐增大,但P支与R支强度则随着电场强度的增大相应地减小,因此可以利用摆动光谱的Q支相对强度(即Q支光谱强度与P,Q,R支光谱总强度的比值)来表示电场强度的大小。同时,计算了电场强度大小与分子取向度的关系,发现分子取向度随电场强度的增大而逐渐增大。通过进一步计算,给出了分子取向度与其摆动光谱的Q支相对强度的关系,并提出采用摆动光谱的Q支相对强度实现分子取向度测量的新方法。

A new method to measure the orientation of cold polar linear molecules using the relative intensity of the Q branch spectrum of the pendular state of linear molecules is presented. The relationship between the orientation of HCN-N~ and Q-branch intensity of pendular state spectrum of the C--H stretch of the ground state of HCN-N2 is studied, and it is found that the intensity of its Q branch spectrum increases with the increase of the electric field strength, but the intensity of the R- and P- branches decreases with the increase of the electric field strength. The relative intensity of the Q branch spectrum （ratio of spectral intensity of Q branch and total intensity of P, Q, R branches） can be used to represent the electric field intensity. Also, the study shows the orientation of the molecule increases with the increase of electric field strength. So it is proposed that the method which uses the relative intensity of the Q branch spectrum can be applied to measure the orientation of the polar molecule.