Theoretical Study Of Electrostatic Trap For Cold Polar Molecules

Cold molecules have some important applications in study of basic physics problems, high-resolution spectroscopy and precise measurement, cold chemical reaction and cold collision, interferometer of matter wave, and quantum computing and information possessing and so on, so the study on the generation and application of cold molecules has obtained fast development. In this thesis, firstly, the basic principle, experimental results and the recent progress on cooling, trapping and manipulating of neutral molecules have been briefly introduced. Secondly, we give the theoretical study of two new trapping schemes for cold poplar molecules.finally, our research work is summarized and the future investigation is briefly speculated later.We propose a new scheme to realize electrostatic trap for cold poplar molecules by using an electrostatic field generated by the combination of a pair of parallel transparent electrodes (i.e., two infinite transparent pates) and a ring electrode (i.e., a ring wire). When the positive voltage is applied on the circular wire, and one of the transparent electrodes is not charged, another is grounded, an electrostatic well in free spare will be formed. If cold polar molecules in the low-field-seeking state are loaded into this trap, they will feel a dipole gradient force due to the first-order Stark effect, and then the cold molecules will be repelled to the minimum of the electric field and caught in the trap. We use commercial finite element software to calculate the relationships between the spatial distribution of the electrostatic field of our charged wire layout (including the distribution of the corresponding Stark trapping potential for CO molecules) and the geometric parameters, and study the dependences of the trap centre position on the system parameters. We also analyze the advantages of the scheme from several aspects, and propose an effective loading way. Our study shows that if we change the geometric parameters, we can both change the position of the trapping center and the depth of the well, which may open a new way to study cold molecular spectroscopy, cold collisions, dipolar-dipolar interaction and collective quantum effects in molecular system, even to realize efficient evaporative cooling of the trapped molecules by lowering the Stark trapping potential, and so on.Based on the first scheme, we also propose another novel electrostatic trapping scheme (i.e., a controllable electrostatic double-well trap) by using two charged ring wires and two parallel transparent electrodes. The spatial distributions of the electrostatic fields from the above charged wires and the charged transparent electrodes for the different geometric parameters and the corresponding Stark potentials for cold CO molecules are also calculated. We study the relationships between the position of the trapping center and the system parameters, and analyze the evolution of our trap from a double-well trap to a single-well one, and discuss the potential applications of the present scheme in molecular interference, molecular entanglement, and molecular collisions, even to study the molecular BEC in the double-well trap, and so on.