Quantum-State-Selection
Quantum-State-Selection
复制标题
量子态选择
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
G. Meijer
中科院分区：
文献类型：
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作者：
J. Nielsen;L. Holmegaard;J. L. Hansen;J. Maurer;Frank Filslnger;J. Küpper;G. Meijer
我们证明了利用强非均匀电场来空间分散分子的旋转态[ I，2]。在实验中，碘苯分子的超声束形成，随后分散在电场中。然后使用聚焦的ns YAG激光器对准分子，或者使用激光器和静电场的组合定向分子。用强烈的飞秒激光脉冲电离分子，并使用速度图图像光谱仪检测离子碎片。反冲方向提供了有关分子空间取向的信息。通过移动激光焦点，可以探测不同的旋转状态。状态选择利用了不同转动态经历不同斯塔克位移的事实。碘苯的旋转基态将经历最大的斯塔克位移，因此在电场中将被最强烈地偏转。测量了分子脉冲的偏转轮廓，并与温度为1 K的轨道模拟结果吻合良好。通过选择处于最低旋转状态的分子，即使在适度的激光场下也可以获得更高程度的对准。激光场和弱静电场的结合通过与分子偶极矩的相互作用提升了指向上和指向下的态的简并度。图1示出了增强的对准和定向的示例。第一行示出了对准，而第二行和第三行示出了激光和静电场之间的各种角度f3的取向。在图2中，取向被示出为f3的函数。显然，量子态选择提供了很大的优势，超过70%的分子以相同的方式取向。总之，静电偏转器的使用使我们能够选择最低的旋转量子态。这允许通过激光和静态场创建前所未有的对准和定向
We demonstrate the use ofstrong inhomogeneous electric field to spatially disperse rotational states ofa molecule[ I, 2]. In the experiment a supersonic beam of iodobenzene molecules is formed and subsequently dispersed in an electric field. The molecules are then aligned using a focused ns YAG laser or oriented using a combination of the laser and a static electric field. The molecules are ionized with an intense fs laser pulse and the ionic fragments are detected using a velocity map image spectrometer. The recoil direction provides information about the spacial orientation of the molecules. By moving the laser focus it is possible to probe different rotational states. The state selection uses the fact that different rotational states experience different Stark shifts. The rotational ground state of iodobenzene will experience the largest Stark shift and will therefore be most strongly deflected in the electric field. The deflected profile of the molecular pulse has been measured and agrees well with trajectory simulations with a temperature of 1 K. By selecting molecules in the lowest rotational states a higher degree of alignment can be obtained even at modest laser fields. The combination of a laser field and a weak static electric field lifts the degeneracy of states pointing up and down through the interaction with the molecular dipole moment. Fig 1 shows examples of the enhanced alignment and orientation. The first row shows alignment, while the second and third shows the orientation for various angles f3 , between the laser and static electric field. In fig 2 the orientation is shown as a function of f3 . It is obvious that the quantum-state selection gives a large advantage with more than 70 % of the molecules being oriented the same way. In conclusion the use of an electrostatic deflector enables us to select the lowest lying rotational quantum-states. This allows creation of unprecedented alignment and orientation by laser and static fields