Chen Lipeng, Gelin Maxim F, Domcke Wolfgang
Department of Chemistry, Technische Universität München, D-85747, Garching, Germany.
J Chem Phys. 2019 Jul 21;151(3):034101. doi: 10.1063/1.5105375.
We study the effect of a dissipative environment on the orientational relaxation of a three-dimensional quantum linear rotor. We provide a derivation of the Hamiltonian of a linear rotor coupled to a harmonic bath from first principles, confirming earlier conjectures. The dynamics generated by this Hamiltonian is investigated by the hierarchical equations-of-motion method assuming a Drude spectral density of the bath. We perform numerically accurate simulations and analyze the behavior of orientational correlation functions and the rotational structures of infrared absorption and Raman scattering spectra. We explore the features of orientational correlation functions and their spectra for a wide range of system-bath couplings, bath memory times, and temperatures. We discuss the signatures of the orientational relaxation in the underdamped regime, the strongly damped regime, and the librational regime. We show that the behavior of orientational correlation functions and their spectra can conveniently be analyzed in terms of three characteristic times, which are explicitly expressed in terms of the parameters of the Hamiltonian.
我们研究耗散环境对三维量子线性转子取向弛豫的影响。我们从第一原理出发推导了与简谐浴耦合的线性转子的哈密顿量，证实了先前的推测。通过假设浴的德鲁德谱密度，采用运动方程分层方法研究了该哈密顿量产生的动力学。我们进行了数值精确模拟，并分析了取向关联函数的行为以及红外吸收和拉曼散射光谱的转动结构。我们在广泛的系统 - 浴耦合、浴记忆时间和温度范围内探索取向关联函数及其光谱的特征。我们讨论了欠阻尼 regime、强阻尼 regime 和摆动 regime 中取向弛豫的特征。我们表明，取向关联函数及其光谱的行为可以方便地根据三个特征时间进行分析，这三个特征时间根据哈密顿量的参数明确表示。
