Laser spectroscopic study of formation of alkali-earth and He van der Waals molecules

1.低温下碱土金属原子与He碰撞动力学的光谱研究（1）低温下Mg^<*4>He_n激基复合物的形成在低温He气体中（5- 30 K），用激光激发Mg进入3s3p^1P_1态，观察到了^<*4>MgHe_n激基复合物的形成。发射光谱已被分析使用的理论对潜在的。激基复合物在电子激发态的寿命内在许多三体反应中生长。最后，多达10个He原子附接在Mg原子周围以形成Mg*He_<10>。在Mg_ He碰撞中也观察到了几乎相同的结果<-3>。在这项研究中，我们已经表明，Mg*Hen分子的形成，虽然Mg和He之间的吸引相互作用能很小。(2)Ba^+-He碰撞动力学我们用激光光谱方法研究了Ba ~+6p^2P_&lt;3/2&gt;态与He原子碰撞的弛豫过程。得到了Ba ~+·He的生成和解离速率常数以及Ba ~+和Ba ~+·He碰撞的精细结构变化。在Ba ~+*He激基复合物形成截面上观察到的类共振结构表明了两步Lindemann机理。我们还观察到在低温下精细结构变化碰撞截面的特殊增加。这表明在低温条件下打开了另一条精细结构变化的通道.我们测量了室温下碱土金属离子与He、H_2和D_2碰撞的精细结构变化碰撞截面。我们发现，与He原子的碰撞截面随精细结构分裂呈指数下降，这可以用绝热跃迁的Landau-Zener模型来解释。与此相反，由于氢分子精细结构的分裂和旋转之间的共振，氢分子的横截面大大增大。

1. Spectroscopic study of alkali-earth atom - He collision dynamics in low temperature(1) Formation of Mg^<*4>He_n exciplex in low temperatureWe have observed the formation of ^<*4>MgHe_n exciplexes by means of laser excitation of Mg into the 3s3p ^1P_1 state in low temperature He gas (5-30K). Emission spectra have been analyzed using a theoretical pair potential. Exciplexes grow in many three-body reactions within its lifetime in the electronic excited state. Finally up to ten He atoms are attached around to a Mg atom to form a Mg*He_<10>. We have also observed almost the same results for Mg_<-3>He collisions. In this research, we have shown that the Mg*Hen molecules are formed although attractive interaction energy between Mg and He is small.(2) Collision dynamics of Ba^<+>-HeWe have investigated the relaxation process of Ba+ in the 6p ^2P_<3/2> state in collision with He atoms using laser spectroscopic method. We have obtained the rate constants of the formation and dissociation of Ba+*He, and the fine structure changing collision of Ba+ and Ba+*He. The resonance like structure observed in the cross section of the formation of Ba+*He exciplex indicates the two-step Lindemann mechanism. We have also observed a peculiar increase in the cross section of the fine-structure changing collision at the low temperature. This indicates another channel of the fine-structure change opens in the low temperature.2. Fine-structure changing collision of alkali-earth ionWe have measured the fine-structure changing collision cross sections of alkali-earth ions at room temperature in collision with He, H_2 and D_2. We have found that cross sections for collisions with He atoms decrease exponentially with the fine-structure splitting, which can be explained by the Landau-Zener model of the adiabatic transition. In contrast to this, cross sections for hydrogen molecules are much enlarged due to resonance between the fine-structure splitting and the rotation of hydrogen molecule.