The Investigation Of Pendular Spectra Of Cold Molecules And Its Applications

This thesis mainly studied the pendulum spectroscopy of three types of cold molecules including the linear ones, the symmetric top ones and the asymmetric top ones under the strong electrostatic field. In addition, we also studied some phenomena, such as energy level shifts, orientation, the orientation of the ensemble, the adiabatic and nonadiabatic addition of electric field. Another important part of this thesis is we proposed a novel approach to measure an electrostatic-field vector and its spatial distribution by using high-sensitive pendular-state spectra of cold linear molecules.The theoretical treatment of cold molecules under a strong electric field is not the same as perturbation theory. The calculation procedure in this theise based on the nonzero matrix elements to reduce computing time. For the calculation of the nearly asymmetric top molecules, it needs just a few minutes to get rotational spectra simulationuses. In addition to that, some preliminary program preparation of cold molecules arranged in the laser field have also been done in this paper.There is no very convenient way of measuring the static electric field vector, we propose a novel approach to measure an electrostatic-field vector and its spatial distribution by using high-sensitive pendular-state spectra of cold linear molecules, and study the dependences of the Q-branch spectrum intensity of cold linear molecules in the electrostatic field on both the electric-field strength and the molecular rotational temperature for different linear molecules. Our study shows that with the increase of electric-field strength from zero, the integrated intensity of the Q-branch spectrum of cold linear molecules will be first fast increased from zero, and then slowly reach saturation, and the lower the molecular rotational temperature is, the higher the Q-branch intensity will be at the same electric-field strength, which can be used to sensitively measure the electric-field vector and its spatial distribution by changing the polarization direction of a focused probe beam. We also find that a multi-peak structure in the Q-branch spectrum will be occurred when the Stark interaction strength ω=μE/B≥61is larger than a critical value, which results from a slight difference of the molecular parameters (μ, B) of the upper and lower vibrational ground states. Finally, we briefly discuss the feasibility of the proposed electric-field measuring scheme and find that our testing method can cover a wide range from10-2V/cm to105V/cm, and the corresponding spatial resolution can reach～10μm.