原子非序列双电离的多次返回碰撞电离机理分析

本文采用三维半经典再散射模型研究了He原子在高光强(1.5×10¹⁵ W/cm²)、少周波激光脉冲作用下的非序列双电离问题,重点分析了沿激光电场极化方向的动量关联谱.发现两个电子沿相反方向发射的比例明显比中等光强区(7×10¹⁴ W/cm²)和低光强区(2.5×10¹⁴ W/cm²),以及同等光强的长脉冲情形都偏高, 同时V形结构也更加明显.通过轨道"回溯"分析, 进一步深入 关键词： 强场 非序列双电离 再散射     

Attosecond transient absorption spectroscopy:Comparative study based on three-level modeling

In the present paper, the time-resolved transient absorption spectroscopy of helium atoms is investigated based on the three-level modeling. The helium atoms are subjected to an extreme ultraviolet(XUV) attosecond pulse and a time-delayed infrared(IR) few-cycle laser field. The odd excited state are populated from the ground state by the XUV pulse due to the dipole selection rule, and probed by the time-delayed IR laser. The time-resolved transient absorption spectroscopy based on the different coupling mechanism demonstrate some different features, the photoabsorption spectrum based on three-level model with rotating wave approximation(RWA) cannot repeat the fast oscillation and the sideband structure which have been observed in the previous experimental investigation. The dressing effect of IR laser pulse on the ground state can contribute new interference structures in the photoabsorption spectrum.     

飞秒强激光场中的原子、分子——非微扰现象研究

文章简要回顾了飞秒强激光场中的原子、分子这一研究领域在近年来所取得的一系列里程碑式的重大发现,包括多光子电离、阈上电离、隧穿电离、越垒电离、非顺序双电离、电离稳定化、高次谐波发射等等非微扰现象.讨论了纯量子理论和纯经典方法在处理该类问题时经常遇到的困难.介绍了作者所在小组为此提出的半经典模型及其在解释强场物理现象时所取得的成果.最后对这一领域在未来几年内的可能发展方向作了简单的评述.     

Dynamical instability and adiabatic evolution of the atom--homonuclear--trimer dark state in a condensate system

This paper investigates the dynamical instability and adiabatic evolution of the atom--homonuclear--trimer dark state of a condensate system in a stimulated Raman adiabatic passage aided by Feshbach resonance. It obtains analytically the regions for the appearance of dynamical instability caused by the interparticle interactions. Moreover, the adiabatic property of the dark state is also studied in terms of a newly defined adiabatic fidelity. It shows that the nonlinear collisions have a negative effect on the adiabaticity of the dark state and hence reduce the conversion efficiency.     

非线性Rosen-Zener跃迁

研究了非线性两模系统的Rosen-Zener跃迁.在绝热近似下，对基态能相同的两个模态，非线性相互作用使原子表现出强烈的集体行为，它们总是趋向于聚集到同一个模态上.因此外场的绝热调制能够把原子从一种模式彻底转移到另一种模式上.在经典相空间中，可以成功地解释该现象.提议利用现有的玻色爱因斯坦凝聚实验观测这一效应. 关键词： Bose-Einstein凝聚 Rosen-Zener跃迁 Rabi振荡 受激Raman绝热暗通道