Numerical Tests of a Fixed Vibrational Basis/Gaussian Bath Theory for Small Molecule Dynamics in Low-Temperature Media

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• 作者：Craig T. Chapman ; Xiaolu Cheng ; Jeffrey A. Cina
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：April 28, 2011
• 年：2011
• 卷：115
• 期：16
• 页码：3980-3989
• 全文大小：1075K
• 年卷期：v.115,no.16(April 28, 2011)
• ISSN：1520-5215

文摘

A recently framed quantum/semiclassical treatment for the internal nuclear dynamics of a small molecule and the induced small-amplitude coherent motion of a low-temperature host medium (Chapman, C. T.; Cina, J. A. J. Chem. Phys.2007,127, 114502) is further analyzed and subjected to initial tests of its numerical implementation. In the illustrative context of a 1D system interacting with a 1D medium, we rederive the fixed vibrational basis/Gaussian bath (FVB/GB) equations of motion for the parameters defining the Gaussian bath wave packet accompanying each of the energy eigenkets of the quantum mechanical system. The conditions of validity for the Gaussian-bath approximation are shown to coincide with those supporting approximate population conservation. We perform initial numerical tests of the FVB/GB scheme and illustrate the semiclassical description it provides of coherent motion in the medium by comparing its predictions with the exact results for a high-frequency system harmonic oscillator bilinearly coupled to a lower-frequency bath oscillator. Linear vibronic absorption spectra or, equivalently, ultrafast wave packet interferometry signals are shown to be readily and accurately calculable within the FVB/GB framework.