The Collision Cross Section of Ultracold Rb Atoms Using Magneto-Optic and Magnetic Traps
|School||Harbin Institute of Technology|
|Keywords||Laser cooling and capture MOT Magnetic trap Collision cross section The depth of the potential well|
Open a new chapter in the development of laser cooling and confinement techniques for the study of atoms, molecules and photophysics. Ultracold atomic collisions great deal of concern by the people as one of the topics at the forefront of the cold atom physics research. Ultracold atomic collisions, atom collision cross-section study is a hot research topic. The collision cross-section of the particle size to reflect the size of the particle collision possibility. Through the study of particle collision cross section, it is possible to obtain the number of particles to be captured in the atomic cooling and BEC experiments, the loss rate of particles, particle two-body and multi-body collision parameters, cold atomic potential well depth of ultracold atomic physics The study has a very important role. The purpose of this paper is to study the the MOT magnetic trap super cold Rb atoms and background gas (Ar, He) collision experiment, proposed a measure of cold atom collision cross-section of the new technology. Rb-cold atoms with background gas collisions to expand experimental and theoretical studies. The main contents of the thesis is as follows: the proposed MOT and magnetic trap ultracold 87Rb atoms at room temperature background gas 40Ar collisions measurement fully collision cross-section of the new technology. MOT and magnetic trap, the technology can accurately measure the loss rate, collision cross section of ultracold Rb atoms under different background gas density. You can use this technology as a standard method of measuring the collision cross section of ultracold atoms. MOT and magnetic trap system is the important part of the collision cross section measurement experiments. The experimental setup including vacuum systems, laser systems and laser frequency stabilization system and Rb cold atom source three main components. The experiment is controlled by computer software to achieve cooling the laser to turn on or off, a simple realization of the magneto-optical trap and the switching of the magnetic trap. Cold atom collision cross section measurement techniques, MOT and magnetic trap, the Rb atoms two isotopes 85Rb and 87Rb inert gases Ar and He collision study. The experimental study found that the loss of Rb cold atom collisions with inert gas, the collision cross section MOT and magnetic trap are very different. Atomic collision physics theory, fractional step fitting calculated collision cross section, the loss rate of the average speed of the LJ potential function coefficients, potential well depth, the evolutionary relationships of the the collision speed collision energy parameters; through theoretical calculations and experimental measurements of the collision section, the value of the loss rate of the average speed found basically consistent with the theoretical and experimental values ??and the theoretical calculation of the collision cross-section, the loss rate of the average speed of the depth of the potential well, you can get the depth of the potential well under the experimental magnetic field conditions can not be reached collision cross section or the loss rate of the average speed value. The theoretical calculation of the loss rate of the average speed and the depth of the potential well is proposed 87Rb cold atoms at room temperature 40Ar background gas collisions between MOT and magnetic trap new method to measure the depth of the potential well. Rb cold atom determine the potential well depth measurement using laser optical trap catalytic operation more simple, only need to measure order collisions between Rb atoms with background gas loss rate Γ, to avoid loss of collisions between the measurement of cold atoms the ratio β, require a higher impact on the atomic density, measuring the depth of the potential well under the conditions of the atom density is low; this method can measure the depth of the potential well in the MOT and the magnetic trap, and expand the measuring range of the depth of the potential well. Finally, cavity quantum electrodynamics is the frontier of the cold atomic physics. The k photon Jaynes-Cummings cavity QED model and sports atomic interaction entropy relationship and entanglement properties. Found that the entropy exchange between atoms and light field characteristics. Atomic motion and photon number and field mode structure of the atom and cavity field entropy relationship. In addition, we discuss the relationship between entropy exchange and entanglement of atomic and field systems.