Xu Nan, Wu Chengyin, Gao Yunan, Jiang Hongbing, Yang Hong, Gong Qihuang
State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing, People's Republic of China.
J Phys Chem A. 2008 Jan 31;112(4):612-7. doi: 10.1021/jp075728h. Epub 2008 Jan 9.
An apparatus was constructed to experimentally quantify the field-free alignment of diatomic molecules irradiated by strong femtosecond laser pulses. In this apparatus, both homodyne and pure heterodyne detections were realized. The alignment signal is proportional to <cos(2)theta> - 1/3 for homodyne detection and (<cos(2)theta> - 1/3) for pure heterodyne detection, where theta is the polar angle between the molecular axis and the laser polarization direction. Fourier transform spectra of the homodyne signal and the pure heterodyne signal were also studied. By comparing the alignment signal and its Fourier transform spectrum with the numerical calculation of the time-dependent Schrödinger equation, we demonstrated that the pure heterodyne signal directly reproduced the alignment parameter <cos(2)theta>, and its Fourier transform spectrum provided information regarding the populations of different J states in the rotational wavepacket.
构建了一种装置，用于通过实验定量强飞秒激光脉冲辐照下双原子分子的无场取向。在该装置中，实现了零差检测和纯外差检测。对于零差检测，取向信号与<cos(2)θ> - 1/3成正比，对于纯外差检测，取向信号与(<cos(2)θ> - 1/3)成正比，其中θ是分子轴与激光偏振方向之间的极角。还研究了零差信号和纯外差信号的傅里叶变换光谱。通过将取向信号及其傅里叶变换光谱与含时薛定谔方程的数值计算进行比较，我们证明纯外差信号直接再现了取向参数<cos(2)θ>，其傅里叶变换光谱提供了有关旋转波包中不同J态布居的信息。
