Study On Molecular Orientation And Pendular Spectroscopy

This paper mainly studied the pendular spectroscopy and orientation of polarized linear molecules, symmetric-top and antisymmetric-top molecules in a strong static field. We propose a method to measure molecular orientation by using Q-branch relative intensity of pendular spectroscopy.Q-branch reltative intensity of pendular spectroscopy can be used to measure the electric field intensity which corresponding to molecular orientation, so we can get the relations of Q-branch relative intensities of pendular spectroscopy and molecular orientations. We calculate the HCN-N2 molecule in rotational temperature of 0.25 K, 5 K and 20 K respectively, and get the relations of Q-branch relative intensities of pendular spectroscopy and molecular orientations. Since the responses of different molecules with electric field strength are different, we calculate three different linear molecules:(HCCCN)3, HCN-N2 and HC1 under rotational temperature 1 K,5 K and 77 K respectively. Symmetric-top and antisymmetric-top molecules also have the same trend of Q-branch relative intensity with electric field as linear molecules, we can use the pendular spectroscopy of symmetric-top and antisymmetric-top molecules to measure molecular orientations. Also, we calculate the relation between Q-branch relative intensityies and orientation of the symmetric-top molecule CH3I and the antisymmetric-top molecule C2H2-HF.Finally, this paper introduce the experimental progress of detecting electric field vector by pendular spectroscopy. We compile the Labview program to synchronize the laser and detected singal. In the process, we met some difficulties in the progress of programming, such as we need to ask for many times to get the data, so we write the loop to ask, etc.