Control of three-dimensional electron vortices from femtosecond multiphoton ionization
Control of three-dimensional electron vortices from femtosecond multiphoton ionization
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DOI：
10.1103/physreva.96.043426
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发表时间：
2017-10
影响因子：
2.9
通讯作者：
Dominik Pengel;S. Kerbstadt;L. Englert;T. Bayer;M. Wollenhaupt
中科院分区：
文献类型：
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作者：
Dominik Pengel;S. Kerbstadt;L. Englert;T. Bayer;M. Wollenhaupt
我们报告了原子飞秒多光子电离中三维（3D）电子涡流的创建和操纵。涡旋形光电子动量分布是由两个具有不同磁量子数的时滞自由电子波包的叠加产生的。在实验中，由偏振型超连续谱源产生的一对延时反向旋转圆偏振（CRCP）飞秒激光脉冲用于电离钾原子。由此产生的 3D 电子涡流是根据一组速度图成像测量结果通过断层扫描重建的。通过改变 CRCP 脉冲序列的时间延迟、螺旋度和光谱带宽，我们可以控制径向涡旋形状。连续体中另一个光子的吸收将阈值涡旋的 ${c}_{6}$ 方位对称性更改为 ${c}_{8}$ 以实现阈值以上电离。来自非微扰激发的电子涡旋显示出 ${c}_{4}$ 方位角对称性和极地方向上的 $\ensuremath{\pi}$ 相位跳跃。叠加态相对相位的确定使我们能够重建自由电子波函数。
We report on the creation and manipulation of three-dimensional (3D) electron vortices from femtosecond multiphoton ionization of atoms. Vortex-shaped photoelectron momentum distributions arise from the superposition of two time-delayed free-electron wave packets with different magnetic quantum numbers. In the experiment, pairs of time-delayed counter-rotating circularly polarized (CRCP) femtosecond laser pulses, generated from a polarization-shaped supercontinuum source, are used to ionize potassium atoms. The resulting 3D electron vortices are reconstructed tomographically from a set of velocity map imaging measurements. By variation of the time delay, the helicity, and the spectral bandwidth of the CRCP pulse sequence, we control the radial vortex shape. Absorption of another photon in the continuum changes the ${c}_{6}$ azimuthal symmetry of the threshold vortex into ${c}_{8}$ for above-threshold ionization. Electron vortices from nonperturbative excitation show ${c}_{4}$ azimuthal symmetry and a $\ensuremath{\pi}$-phase jump in the polar direction. Determination of the relative phase of the superposition state allows us to reconstruct a free-electron wave function.