铯47D精细能级超冷里德堡原子自由演化的动力学研究∗

摘要

利用连续窄线宽激光器将超冷铯原子分别激发到47D3/2,47D5/2精细态,观察了处于里德堡精细态的铯原子向超冷铯等离子体自由演化的过程,详细对比了不同精细态的铯里德堡原子预电离时间、电离速率以及等离子体的转化效率。里德堡原子快速转化为等离子体的过程被解释为局域势阱内由预电离产生的电子与里德堡原子的快速碰撞导致的雪崩电离。%The spontaneous evolution from Rydberg atoms in different fine states to plasmas is investigated. Two-photon excitation is used to excite ultracold cesium atoms from 6S1/2 to 47D3/2 and 47D5/2 Rydberg states, respectively. The ramp electric field is used to ionize the Rydberg atoms and drive the ions to the micro-channel plate detector. In this experiment, the atom number of 47D5/2 state, which has a high oscillator strength compared with 47D3/2, is about 7 times larger than that of 47D3/2 state. Based on the different initial atom numbers of two fine states, the evolutions of plasma and Rydberg atoms are observed. The initial ionization time of Rydberg atoms and avalanche ionization rate of different states are presented. The initial ionization of Rydberg atoms is ascribed to the combining effect of state transfer from repulsive interaction to attractive interaction induced by the blackbody radiation and superradiation and Rydberg atoms collision. Moreover, the avalanche ionization and production of plasma are explained as being due to the rapid collision between Rydberg atoms and electrons in a local potential trap produced by positive ions.