【作者】 徐静；

【导师】 景辉；

【作者基本信息】 河南师范大学 ， 光学， 2015， 硕士

【摘要】 从玻色-爱因斯坦凝聚理论提出,到二十世纪末在实验上成功形成BEC,足足经历了七十年,这是一个漫长而枯燥的过程,但是随着BEC在实验上的形成,这极大的鼓舞了科学家的内心,凡是有关玻色—爱因斯坦凝聚的研究都深深地吸引了物理学界研究者的目光。在形成BEC的过程中,需要两个很重要的条件,首先就是降低系统温度,让其低于给定密度下临界温度,其次就是提高系统粒子密度,让其超过给定温度下临界密度。在形成BEC的过程中,也发展了多种先进的技术,尤其是利用激光捕获和冷却原子,这是BEC研究史上的一大突破,改变了最初实验研究的重点。BEC的研究和发展,促进了人们去了解原子内部结构,增加了对原子的新的认识。随着BEC进一步的发展,人们开创了很多新的技术来形成BEC,比如光缔合（PA）技术,随后的费什巴克共振（Feshbach）辅助光缔合技术,叶菲莫夫（Efimov）共振辅助光缔合技术等,人们利用这些技术制备出了很多新的分子。分子BEC凝聚体在相干光信息存储、光波群速度减慢、量子计算、非线性、量子通信、量子信息处理和量子原子光学都有广阔的应用前景。BEC的形成还开辟了超化学研究的领域,制备出了很多仅依靠化学反应不能制备的分子,增加了分子的种类,为制备新分子和进行研究打开了一扇新的大门。BEC凝聚态还有很多用途,比如制造原子钟,形成慢光,制造量子计算机等,这都将促进人类社会的文明。BEC的研究正在发生着翻天覆地的变化,促进了社会的进步和发展。近年来,人们更多的是利用叶菲莫夫共振辅助激发绝热通道来形成BEC,为BEC的形成提供了更多的灵活性,也正是如此,形成的多聚物的转化效率得到很大提高,但是BEC的形成还是不能达到商业上的生产要求,因此商业价值还是不是很高。在本文中,主要详述了形成BEC的理论原因,形成BEC的技术手段,以及介绍了叶菲莫夫凝聚态,随后从理论计算上介绍了利用广义叶菲莫夫共振暗态形成分子⁴¹K₂⁸⁷Rb₂,虽然研究的是暗态,但在这里有两个通道可以形成⁴¹K₂⁸⁷Rb₂,所以就可以通过单通道和双通道(同时来形成⁴¹K₂⁸⁷Rb₂的两个通道)来形成⁴¹K₂⁸⁷Rb₂,在研究过程中,发现在双通道中形成⁴¹K₂⁸⁷Rb₂的粒子数远远大于在单通道中形成的粒子数。最后还研究了一下粒子数不平衡对原子-分子转化率的影响,发现当原子数目的比例是一比一的时候,原子分子转化率是最高的,而且发现还可以把这个方案推广到形成费米异核四聚体。更多还原

【Abstract】 From the proposing of Bose- Einstein condensate theory to successful formation of BEC in the experiment in the early twentieth century, a full seventy years of experience, this is a long and tedious process, but with the formation of BEC in the experiment, which greatly encouraged the scientist’s heart, all about the Bose- Einstein condensates study physics community deeply attracted the attention of researchers. In the process of the formation of the BEC, it has two very important conditions, the first is to reduce the system temperature to below the critical temperature for a given density, followed by the particle density to improve the system so that the critical density exceeds a given temperature. In the process of the formation of BEC, we develop a variety of advanced technology and especially the use of laser capture and cool atoms, which is a major breakthrough in the history of BEC research, changing the focus of the first experimental study. With research and development of BEC, it promotes the people to understand the internal structure of atoms and an increase of atoms in a new understanding. With the further development of BEC, it created a lot of new technology to form a BEC, such as light association（PA） technique, followed Feshbach resonance auxiliary light associative techniques, Efimov resonance auxiliary light associative techniques and people use these technologies to create a lot of new molecules. Molecular BEC has broad application prospects in the coherent optical information storage, slow group velocity of light waves, quantum computing, nonlinear and quantum communication, quantum information processing and quantum atom optics. BEC formation has also opened up the field of super-chemical research, prepared a lot of chemical reactions can not rely solely on the creation of molecules, increasing the types of molecules.With the creation of new molecules and study,it opens a new door. BEC condensed matter has many uses, such as manufacturing atomic clock, the formation of slow light manufacturing quantum computers, which will promote the civilization of human society. BEC research is undergoing tremendous change, promoting social progress and development. In recent years, people prefer to use a Efimov-resonance assisted stimulated adiabatic passage to form BEC, for the formation of BEC provides more flexibility, and the conversion efficiency of the condensate formed greatly improved, but still it can not reach BEC formed commercial production requirements, so the commercial value is not very high. In this paper, the main contents include the reason for the formation of theory of BEC, BEC formation techniques, and introduces the Efimov condensed matter, and then describes the use of the generalized Efimov resonance dark forming molecules ⁴¹K₂⁸⁷Rb₂ from theoretical calculations, although study the dark state, there are two channels can form the moleculars⁴¹K₂⁸⁷Rb₂, so you can through a single-channel and dual-channel to form⁴¹K₂⁸⁷Rb₂(two channels at the same time to form⁴¹K₂⁸⁷Rb₂), in the course of the study, found that the number of the particles formed in the dual channel is far greater than the number of particles in a single channel formed. Finally, the number of particles is a little unbalanced which affects atom- molecule conversion rate, and found that when the number of atoms in a ratio of one to one, atomic and molecular conversion rate is the highest, but also found the program is extended to form a fermi heteronuclear tetramer.更多还原