Instituto Carlos I de Física Teórica y Computacional and Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, 18071 Granada, Spain.
Phys Chem Chem Phys. 2011 Nov 14;13(42):18815-24. doi: 10.1039/c1cp21195a. Epub 2011 Jun 29.
We present a theoretical study of recent laser-alignment and mixed-field-orientation experiments of asymmetric top molecules. In these experiments, pendular states were created using linearly polarized strong ac electric fields from pulsed lasers in combination with weak electrostatic fields. We compare the outcome of our calculations with experimental results obtained for the prototypical large molecule benzonitrile (C(7)H(5)N) [J. L. Hansen et al., Phys. Rev. A, 2011, 83, 023406.] and explore the directional properties of the molecular ensemble for several field configurations, i.e., for various field strengths and angles between ac and dc fields. For perpendicular fields one obtains pure alignment, which is well reproduced by the simulations. For tilted fields, we show that a fully adiabatic description of the process does not reproduce the experimentally observed orientation, and it is mandatory to use a diabatic model for population transfer between rotational states. We develop such a model and compare its outcome to the experimental data confirming the importance of non-adiabatic processes in the field-dressed molecular dynamics.
我们对最近的非对称陀螺分子的激光对准和混合场定向实验进行了理论研究。在这些实验中， pendular 态是通过使用脉冲激光的线性偏振强交流电场与弱静电场相结合而产生的。我们将我们的计算结果与为原型大分子苯甲腈（C（7）H（5）N）获得的实验结果进行了比较[J.L.Hansen 等人，Phys.Rev.A，2011，83，023406]，并探索了几种场配置下分子系综的方向特性，即交流和直流场之间的不同场强和角度。对于垂直场，得到了纯对准，这与模拟结果吻合得很好。对于倾斜场，我们表明，过程的完全绝热描述不能再现实验观察到的取向，并且必须使用旋转态之间的人口转移的非绝热模型。我们开发了这样一个模型，并将其结果与实验数据进行比较，证实了非绝热过程在分子动力学中的重要性。
