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首页> 外文期刊>The Journal of Chemical Physics >Linear absorption spectrum of a quantum two-dimensional rotator calculated using a rotationally invariant system-bath Hamiltonian
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Linear absorption spectrum of a quantum two-dimensional rotator calculated using a rotationally invariant system-bath Hamiltonian

机译：使用旋转不变的系统浴室汉密尔尼计算量子二维旋转器的线性吸收光谱

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摘要

We consider a two-dimensional rigid rotator system coupled to a two-dimensional heat bath. The Caldeira-Leggett (Brownian) model for the rotator and the spin-Boson model have been used to describe such systems, but they do not possess rotational symmetry, and they cannot describe the discretized rotational bands in absorption and emission spectra that have been found experimentally. Here, to address this problem, we introduce a rotationally invariant system-bath (RISB) model that is described by two sets of harmonic-oscillator baths independently coupled to the rigid rotator as sine and cosine functions of the rotator angle. Due to a difference in the energy discretization of the total Hamiltonian, the dynamics described by the RISB model differ significantly from those described by the rotational Caldeira-Legget model, while both models reduce to the Langevin equation for a rotator in the classical limit. To demonstrate this point, we compute the rotational absorption spectrum defined by the linear response function of a rotator dipole. For this purpose, we derive a quantum master equation for the RISB model in the high-temperature Markovian case. We find that the spectral profiles of the calculated signals exhibit a transition from quantized rotational bands to a single peak after spectrum collapse. This is a significant finding because previous approaches cannot describe such phenomena in a unified manner. Published by AIP Publishing.
机译：我们考虑一个二维刚性旋转器系统，耦合到二维热浴。对于转子和自旋玻色子模型的卡尔代拉-莱格特（布朗）模型已被用于描述这样的系统，但它们不具有旋转对称性，并且它们不能描述在吸收和发射光谱的离散转动带已发现实验。在这里，为了解决这个问题，我们引入了一种旋转不变的系统浴（RISB）模型，该模型由两组谐波振荡器浴，独立地耦合到刚性旋转器，作为旋转器角度的正弦和余弦功能。由于在总哈密顿能量离散化的差，由RISB模型中描述的动力学从那些由旋转卡尔代拉-莱格特模型描述不同显著，而这两种模式减少到Langevin方程在经典极限一个旋转器。为了证明这一点，我们计算由旋转器偶极子的线性响应函数限定的旋转吸收光谱。为此目的，我们在高温市场案例中获得了RISB模型的量子母部方程。我们发现计算信号的光谱分布表现出从量化旋转带的过渡到频谱塌陷后的单个峰。这是一个重要的发现，因为之前的方法无法以统一的方式描述这种现象。通过AIP发布发布。

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