School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
J Chem Phys. 2013 Jul 28;139(4):044305. doi: 10.1063/1.4816121.
The field-free orientation induced by a single-cycle terahertz (THz) laser pulse is studied for two "heavy" molecules, NaI and IBr. Two methods are used and compared in the calculations: One is to solve the exact time-dependent Schrödinger equation (ETDSE) considering the full-rovibrational degrees of freedom, and the other is to invoke the rigid-rotor approximation (RRA). Calculations are performed for the central frequency varying from 0.05 to 1.0 THz and for the peak intensity taken to be 5 × 10(7), 2 × 10(8), and 5 × 10(8) W∕cm(2), respectively. The degree of field-free orientation, <cosθ>, is strongly dependent on the central frequency and the peak intensity of the single-cycle THz pulse. The maximum degree of field-free orientation is determined to be 0.84 for NaI and 0.63 for IBr in these given ranges of frequency and intensity. The molecular orientation obtained by the RRA calculations is in good agreement with that obtained by the ETDSE in the given parameter region.
我们研究了单个太赫兹（THz）激光脉冲产生的无场取向，研究对象为两种“重”分子，碘化钠（NaI）和溴化碘（IBr）。在计算中使用了两种方法并进行了比较：一种是求解考虑全振转自由度的精确含时薛定谔方程（ETDSE），另一种是使用刚性转子近似（RRA）。计算的中心频率范围从 0.05 到 1.0 THz，峰值强度分别取为 5×10(7)、2×10(8)和 5×10(8) W∕cm(2)。无场取向的程度<cosθ>强烈依赖于单周期 THz 脉冲的中心频率和峰值强度。在给定的频率和强度范围内，NaI 和 IBr 的最大无场取向程度分别确定为 0.84 和 0.63。在给定的参数区域内，RRA 计算得到的分子取向与 ETDSE 得到的结果非常吻合。
