近日，美国内布拉斯加大学的J. M. Ngoko Djiokap及其i研究小组取得一项新进展。经过不懈努力，他们利用同步交叉啁啾激光脉冲研究类似衔尾蛇图案的电子螺旋。相关研究成果已于2024年3月22日在国际知名学术期刊《物理评论A》上发表。

该研究团队基于电偶极子、激光和旋转波近似的一阶微扰理论，进行了深入解析计算，主要探讨了两个同步交叉线性啁啾脉冲，在特定配置下单光子氢原子单电离的线性过程。在这一配置中，一个脉冲沿另一个圆偏振脉冲的传播方向线性极化。

研究结果显示，当脉冲具有有限或相同的啁啾时，会在光电子动量分布中产生单极（马蹄形）图案。然而，当这些脉冲的啁啾不同时，会呈现出一种独特的单臂可逆螺旋模式，其形态类似于蛇咬自己尾巴的图案，即衔尾蛇图案。

值得注意的是，这种自分裂螺旋的形成和特性可以通过多种方式调控，包括改变啁啾的数量和符号、调整脉冲的持续时间、控制螺旋度以及调节第二脉冲的椭圆度。特别地，当椭圆度小于0.4时，使用椭圆偏振的第二脉冲能够有效破坏这种衔尾蛇螺旋结构。这项研究结果对任何s态原子都是有效的，如本文所示的氢原子和氦原子。

附：英文原文

Title: Ouroboros-pattern-like electron spirals by synchronous crossed chirped laser pulses

Author: L. Pedersen, J. M. Ngoko Djiokap

Issue&Volume: 2024/03/22

Abstract: By means of analytical calculations based on first-order perturbation theory within the electric dipole, laser, and rotating wave approximations, we investigate the linear (in intensity) process of one-photon single ionization of the hydrogen atom by two synchronous crossed linearly chirped pulses in the configuration where one pulse is linearly polarized along the propagation direction of another circularly polarized pulse. We show that transform limited or identically chirped pulses create a monopole (horseshoelike) pattern in the photoelectron momentum distribution, whereas a single-arm reversible spiral resembling the patterns of a snake biting its own tail (Ouroboros patterns) emerges when these pulses are differently chirped. This self-splitting spiral is controlled by varying the amount and sign of chirp, the pulse duration, the helicity, and the ellipticity of the second pulse. We show that the use of an elliptically polarized second pulse can destroy the Ouroboros spirals when the ellipticity is less than 0.4. Our results are valid for any S-state atoms, as illustrated here for the hydrogen atom as well as the helium atom.

DOI: 10.1103/PhysRevA.109.033114

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.033114