Electrostatic Manipulation Of Cold Polar Molecules And Their Stark Deceleration

Getting ever better control over both the internal and external degrees of freedom of gas-phase molecules has been an important theme in molecular physics during the last two decades. Interest in the field of cold molecules is triggered by various potential applications and by the promise of the occurrence of interesting new physics and chemistry with molecules of low temperatures and high densities. This thesis is dedicated to the study of manipulation of cold polar molecules with electrostatic fields, focusing on electrostatic guiding, electrostatic splitting and Stark deceleration of cold polar molecules.We propose a novel scheme of electrostatic guiding of cold polar molecules, which is based on a single charged wire. An analytic expression for electrical field distribution in free space is derived, and the relationships between the electrical field distribution in free space, the Stark potentials of meta-stable CO molecules, their corresponding electrical dipolar gradient force inside the guide and the parameters of the guiding setup are analyzed in detail. A brief introduction about its potential applications in molecule optics is presented as well.Based on the above electrostatic guide, a Y-shaped molecular beam splitter (MBS) is conceived. We analyze the electrical filed distribution inside the MBS, and simulate the dynamics of passing ¹⁵ND₃ molecules of weak-field-seeking state through the MBS using Monte-Carlo method. The splitting ratio of the MBS can be easily adjusted by changing the high voltages applied on the wires of the two output branches.As an efficient technique for production of cold molecules with very low velocities, Stark deceleration has grown rapidly over the years. We calculate the energy structure of CH₃F molecules in external electrical fields as well as the rotational populations of supersonic CH3F molecular beams. A simple analytic model is being used to analyze the motion of weak-field-seeking CH₃F molecules inside the decelerator, including phase stability, slowing efficiency as well as the translational temperature of the decelerated molecular packet. Monte-Carlo simulations are performed for better understanding the dynamics of weak-field-seeking CH3F molecules moving inside the decelerator. Corresponding results are presented in comparison with those from analytical model.Based on theoretical study, we perform Stark deceleration of supersonic CH3F molecular beams in experiment. We build our experimental system from scratch, and carry out a series of study, including the velocity distribution, electrostatic guiding as well as Stark deceleration of supersonic CH3F molecular beams.