Finneran Ian A, Welsch Ralph, Allodi Marco A, Miller Thomas F, Blake Geoffrey A
Division of Chemistry & Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
Division of Geological & Planetary Sciences, California Institute of Technology , Pasadena, California 91125, United States.
J Phys Chem Lett. 2017 Sep 21;8(18):4640-4644. doi: 10.1021/acs.jpclett.7b02106. Epub 2017 Sep 13.
Fundamental properties of molecular liquids are governed by long-range interactions that most prominently manifest at terahertz (THz) frequencies. Here we report the detection of nonlinear THz photon-echo (rephasing) signals in liquid bromoform using THz-THz-Raman spectroscopy. Together, the many observed signatures span frequencies from 0.5 to 8.5 THz and result from couplings between thermally populated ladders of vibrational states. The strongest peaks in the spectrum are found to be multiquantum dipole and 1-quantum polarizability transitions and may arise from nonlinearities in the intramolecular dipole moment surface driven by intermolecular interactions.
分子液体的基本性质由长程相互作用决定，这种相互作用在太赫兹（THz）频率下最为显著地表现出来。在此，我们报告了使用太赫兹-太赫兹-拉曼光谱在液态溴仿中检测到非线性太赫兹光子回波（重相位）信号。综合来看，许多观测到的信号跨越了0.5至8.5太赫兹的频率范围，是由热填充的振动能级阶梯之间的耦合产生的。光谱中最强的峰被发现是多量子偶极和单量子极化率跃迁，可能源于分子间相互作用驱动的分子内偶极矩表面的非线性。
