【作者】 周小岩；

【导师】 沈异凡；

【作者基本信息】 新疆大学 ， 原子分子物理， 2004， 硕士

【摘要】 本论文从实验上深入研究了碱分子激发态(低位激发态及高位态)的预解离过程；激发态原子和分子通过分子预解离和碰撞转移得到布居的过程；激发态分子与基态原子间及激发态分子与激发态原子间的两类碰撞能量转移过程。实验工作：1) 利用He-Cd激光器的441.6nm线光解Cs2分子，使Cs（n2L）（nL=7P，6D）态得到布居，在Cs密度1到9×1015cm-3范围内测量原子荧光对分子荧光强度比，得到碰撞转移率系数对解离率之比分别为3.1×10-17cm3(对7P)和1.2×10-17cm3(对6D)。测定Cs nLJ对nLJ’荧光分支比，得到72P，62D态精细结构解离率之比分别为0.53和0.43。给出了碰撞转移到6D态外（即Cs（6D）+Cs（6S）→Cs（6D）以外的态）的截面为1.9×10-14cm2。精细结构碰撞转移(即Cs（7P1/2）+Cs（6S）→Cs（7P3/2）+Cs（6S）)截面为3.5×10-14㎝2。由计算的72P态几何截面σgeom能够很好地描述σ12和σ21的数量级。2) 用He-Cd激光器的441.6nm线激发Na2分子到B1Πu电子态，记录了Na原子的跃迁和Na2分子的A1Σu+-Χ1Σg+的谱带。由Na与Na2激发态发射的光谱及其强度可以认定在Na－Na2系统中的碰撞过程，Na原子线是Na2（B1Πu）到Na（3P）的碰撞能量转移产生的，预解离过程也可产生原子线。而A1Σu+-Χ1Σg+谱带是由B1Πu到21Σg+的碰撞转移后再由21Σg+到A1Σu+的辐射而引起的。在360℃，根据辐射衰变率和荧光强度，得到Na2（B1Πu）到Na2（21Σg+）碰撞转移率系数为5.7×10-10cm3s-1，而B1Πu的预解离率为2.7×106s-1。3) 用双光子吸收技术研究了Na2高位E态的预解离和Na2（E）与Na之间的碰撞激发转移。Na蒸气温度控制在623K至693K之间，测量激发态Na原子的nL→3P跃迁的荧光强度，得到了各预解离率与碰撞能量转移率系数之比。讨论了其它过程对<WP=4>速率系数的影响。全文共分四章。第一章前言，主要阐述了原子分子碰撞和光谱研究的意义、现状、背景和主要实验工作。通过本章的介绍，我们将对该领域及实验工作有一个概括的了解。第二章说明本论文研究所涉及到的过程、原理及方法。例如辐射，跃迁，解离，碰撞等过程，Franck-Condon 原理，速率方程的建立，激光感生荧光光谱法，双光子吸收光谱。通过本章，我们将了解到光与物质的相互作用性质，并对诸如预解离、碰撞能量合并、Franck-Condon 因子、Morse、RKR等物理概念有所认识，为进入该研究领域作好准备。第三章系统的介绍了实验设备，样品制备系统，检测系统及实验测试方法。第四章对实验结果进行了详细地讨论和分析。在本论文中，采用分子的激光光解和激发态分子与原子的碰撞来产生激发态原子的机制。这两种机制对激发态分子与原子、原子与原子间的碰撞、原子分子间的反应动力学及激发态的输运等起很大作用，为原子分子相互作用势和解释各种辐射现象提供了许多信息。同时，通过这些研究，可以探测分子排斥态，获得激发态分子常数、解离物的态分布。更多还原

【Abstract】 The dissertation is devoted to the analysis and study of three processes in experiment. These are photodissociation process of alkali molecules, population process of the excited states of alkali atoms and alkali molecules populated by predissociation and collision transfer of alkali molecules and two kind of collisional energy transfer process between the excited states of alkali molecules and the excited states of alkali atoms.The results of experiments concerning as follow: 1) Populations of the n2L(nL=7P，6D)states of Cs atoms by photodissociation of Cs2 molecules through the use of the fixed frequency line 441.6nm of a He-Cd laser radiation are produced. Combining ratios of atomic to molecular fluorescence at the Cs density range between 1 and 9×1015cm-3,the ratios of collisional rate coefficient to predissociation rates are estimated to be 3.1×10-17cm3 and 1.2×10-17cm3, respectively. The branching ratios are defined as the ratios of nLJ to nLJ’ fluorescence. The ratios of the dissociation rates produced in n2L fine structure states are 0.53 and 0.43,respectively. The cross section for excitation transfer out of the 6D doublet [i.e., Cs (6D)+Cs (6S) →states other than Cs (6D)] is 1.9×10-14cm2. The cross section for the fine-structure-changing collision [i.e., Cs (7P1/2)+Cs (6S) →Cs (7P3/2)+Cs (6S)] is 3.5×10-14 cm2. The calculated result for the geometrical cross-section <WP=6>of excited Cs 72P state shows that the magnitudes of σ12 and σ21 can be described relatively well by σgeom. 2) The B1Πu electronic state of Na2 is excited by the 441.6nm He-Cd laser line. The Na atomic transitions and the A1Σ+u→X 1Σ+g band of Na2 have been recorded. From the intensities and spectra of the Na and Na2 fluorescence several collisional processes in the excited sodium atom-dimmer system have been identified. The Na atomic lines are the result of collisional energy transfer from the Na2(B1Πu) to the Na(3P).Predissociation process may also contribute to atomic fluorescence. The A1Σ+u→X 1Σ+g band is interpreted through a populating mechanism involving collisional transfer from the B1Πu to the 21Σ+g followed by radiative transfer to the A1Σ+u state. From the decay constants and fluorescence intensities, the rate coefficient at 360℃ for collisional energy transfer from Na2(B1Πu) to Na2(21Σ+g) is 5.7×10-10cm3S-1.The predissociation rate of the B1Πu is 2.7×106S-1. 3) Depopulation mechanisms of a high-lying state of Na2 are studied using the two-photon absorption technique. The temperatures of the Na vapor were in the range from 623K to 693K. The predissociation and collisional transfer are monitored by the atom sodium emission on the nL→3P transition. Rations of various predissociation rates and collisional transfer rate coefficients are obtained. The contributions to the rate coefficients from other processes are discussed.The whole thesis consists of four chapters. Chapter one is a brief overview of predissociation and collision transfer effect on <WP=7>the excited states of alkali atoms and alkali molecules. Modern laser techniques improved the sensitivity and resolution of spectrum detection, and laser spectroscopy method now plays an important role in the molecular spectroscopy studies. This Chapter has explained mainly the meaning, the background, current situation and main research work in which collision and spectrum of atom molecule studied. Chapter two interpreted all kinds of process, several principles and two methods. Process included radiation, transition, dissociation, collision, and so on. This Chapter also interpreted Franck-Condon principle, setting-up of the speed equation, laser-induced fluorescence and two-photon absorption technique. By these illustrations, we can acquire a basic sight on predissociation and collision depopulation mechanisms. Chapter three we designed and set up a highly sensitive and high-resolution experiment facilities. This Chapter introduced experiment apparatus, the system preparing sample, the detected system, experiment course and steps. Chapter f更多还原