Imaging Electrons and Ions produced by two colour Counter rotating laser fields of variable ellipticity

今天的飞秒激光通常达到1014W/cm2的强度范围。暴露在这种激光脉冲下的原子和分子被有效地电离。在振荡激光场的最大值，短电子波包被释放，然后由激光场驱动。因此，整形电场允许引导这些波包，这是优先程序1840的核心。本实验项目将使用非常灵活的波形(400 nm和800 nm两个反向旋转的椭圆场的叠加)。在最简单的构型中，这样的场具有三重对称性，电场矢量类似于三叶三叶草。调节两种颜色之间的相对场强、椭圆度和相对相位打破了这种对称性，并产生了大量不同的场形状。复杂的场形状将产生复杂的电子三维动量分布，它携带了场驱动量子动力学的所有信息。我们将使用COLTRIMS技术测量这些三维电子动量分布。对于每个电子，我们将同时测量离子的电荷态和动量，对于小分子，我们将测量带电分子碎片的方向和能量。场形状的灵活性将使我们了解库仑势和激光场在电离过程中的相互作用。其次，它将允许我们控制在一个周期内不同时间发射的电子波包，使它们受到干扰(周期内干扰)，或者将它们引导到动量空间的不同区域，以避免这些干扰。这些电子波包的干涉图携带了有关电子产生的原子或分子轨道的角度相关相位的信息。我们将用它来探索分子轨道。灵活的场形状将再次允许我们控制电子波包与其母离子重新碰撞的能量分布和方向。我们的模拟表明，即使是几乎单能的电子束也可以通过调节磁场来产生。所提出的场形式的一个特别优点是，重新碰撞的电子可以被引导到相空间的一个区域，在那里它们不会被直接电子淹没。这反过来又允许研究和控制在再碰撞中原本无法达到的特征和能量范围(低能量)。我们将利用这一点来探索激光场中小分子的形状共振。我们还将利用这些电子进行激发、多重电离和驱动分子解离。总而言之，我们将结合最先进的三维电子和离子成像与高度灵活的反向旋转椭圆双色场的形状来研究和控制从原子和小分子发射的电子波包以及与原子和小分子重新碰撞的未呈现的细节和完整性。

Femtosecond lasers today reach routinely intensities in the 1014 W/cm2 range. Atoms and molecules exposed to such laser pulses are efficiently ionized. At the maxima of the oscillating laser field short electron wave packets are set free which are then driven by the laser field. Shaping the electric field thus allows steering theses wave packets, which is at the heart of Priority Program 1840. The present experimental project will use a very flexible waveform (a superposition of two counter rotating elliptical fields of 400nm and 800nm). In the simplest configuration such a field has threefold symmetry, the electric field vector resembles a three leave shamrock. Tuning the relative field strength, the ellipticity and relative phase between the two colours breaks this symmetry and gives rise to a multitude of different field shapes. The complex field shapes will give rise to a complex three dimensional momentum distribution of the electrons which carries all the information on the field driven quantum dynamics. We will measure these three dimensional electron momentum distributions using the COLTRIMS technique. For each electron we will measure in coincidence the ion charge state and momentum and for small molecules the direction and energy of the charged molecular fragments.The flexibility of field shapes will allow us to learn about the interplay of coulomb potential and laser field in the ionization process. It will secondly allow us to steer the electron wave packets emitted at different times during one cycle to bring them to interference (intra cycle interference) or steer them to separate regions of momentum space to avoid these interferences. These interferogramms of the electron wave packets carry information on the angular dependent phase of atomic or molecular orbital from which the electrons emerged. We will use this to explore molecular orbitals. The flexible field shapes will thirdly allow us to control the energy distribution and direction of the electron wave packet recolliding with its parent ion. Our simulations suggest that even almost mono energetic electron beams can be made by tuning the field. A particular advantage of the suggested field forms is that the recolliding electrons can be directed to a region of phase space where they are not swamped by the direct electrons. This in turn allows to study and control otherwise inaccessible features and energy ranges (low energies) in the recollision. We will exploit this to explore shape resonances in small molecules in a laser field. We will furthermore use these electron for excitation, multiple ionization and to drive molecules to dissociation. In summary, we will combine the most advanced 3dimensional electron and ion imaging together with the highly flexible shape of counter rotating elliptical two colour fields to study and control electron wave packets emitted from and recolliding with atoms and small molecules in unpresented detail and completeness.