摘要
碰撞能量转移是物理、化学、生命科学和材料科学等领域的重要研究课题。本论文以X_2(X = Na、Li)分子的缓冲气(buffer gas,通常为He)载带冷却实验为背景,利用量子动力学理论系统地研究了He-Na_2和He-Li_2体系的势能面,碰撞动力学等。
本论文共分四章。第一章简述了分子间弱相互作用的理论计算方法,以及X_2(X = Na、Li)体系动力学研究现状。第二章阐述了分子轨道从头算方法的基本原理和非弹性散射计算的基础理论。第三章,重点从理论上研究了He-Na_2体系势能面的特性及碰撞动力学。第四章,详细讨论了He- Li_2体系势能面的特性并与第三章的He-Na2体系进行了对比,重点比较了两者的异同点,总结出了He - X_2(X = Na、Li)体系势能面和碰撞动力学特点。主要工作体现在以下几个方面:
(1)采用超分子耦合簇理论CCSD(T)方法,对He原子采用aug–cc- pVQZ(7s3p2d1f)/[s3p2d1f]、Na原子用cc-pCVQZ(19s,12p,3d, 2f,1g)/ [6s, 5p,3d,2f,1g]、Li原子用cc-pVQZ (12s6p3d2f1g) / [5s4p3d2f]的原子中心高斯函数,并加入{3s3p2d1f}集的键函数组成的大基组,计算得到了He-Na_2和He-Li_2体系的三维势能面。通过理论计算的结果确认这两个势能面上均存在两个势阱,分别对应于线型构型和T型构型,整个势能面均呈现弱的各向异性。其中He-Na_2体系对应于Na-Na-He线型构型的势阱在θ=0~0、R_m = 14a_0 ,阱深为1.58cm~(-1);T型构型势阱在θ=90~0、
Collisional energy transfer is an important topic in the fields of physics, chemistry, life sciences and material sciences. In this thesis, we have performed systematic studies on quantum dynamics of the He-Na_2 and He-Li_2 system, based on the background of Buffer-gas cooling experiment. It includes the theoretical investigation on the potential energy surfaces and collision dynamics.
This paper is divided into four parts. In chapter one, the development of dynamical studies for the He-X_2(X=Na、He) system are briefly introduced. In chapter two, the basic principle of the molecular orbits ab initio and the theory of the inelastic scattering are presented. In chapter three, the potential energy surface for He-Na_2 system has been calculated. The quantum dynamics are introduced in detail. In chapter four, the potential energy surface for He-Li_2 system has been calculated. It also has two potential wells as the potential energy surface for He-Na2. The whole potential energy surface exhibits weak anisotropic. We discussed the similarities and differences between the two complexes. Our main work is presented as following:
(1) The intermolecular interaction energies corresponding to different He-Na_2 and He-Li_2 configurations have been calculated by
引文
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