范德瓦尔斯团簇有限温度谱的理论研究。I. CaAr_n相变的探测
Theoretical study of finite temperature spectroscopy in van der Waals clusters. I. Probing phase changes in CaAr_n
摘要：
利用各种理论和数值方法研究了热平衡下钙掺杂氩团簇CaAr_n的光吸收谱。温度对吸收光谱的影响，估计使用量子叠加方法的各种团簇尺寸在范围6<=n<=146。在谐波近似水平下，通过Wadi和Pollak的高斯理论的扩展计算吸收强度[J. Chem.Phys.vol 110，11890（1999）]。这个理论是测试简单的，几个原子系统在经典和量子制度，高度准确的Monte Carlo数据可以获得。通过对配分函数和各异构体的权重进行量子非谐修正，我们证明了叠加方法能够正确地描述CaAr_n体系的有限温度光谱性质.在有限尺寸效应下，讨论了吸收光谱作为氩团簇异构化或相变的可能探针的应用。
英文摘要：
The photoabsorption spectra of calcium-doped argon clusters CaAr_n are investigated at thermal equilibrium using a variety of theoretical and numerical tools. The influence of temperature on the absorption spectra is estimated using the quantum superposition method for a variety of cluster sizes in the range 6<=n<=146. At the harmonic level of approximation, the absorption intensity is calculated through an extension of the Gaussian theory by Wadi and Pollak [J. Chem. Phys. vol 110, 11890 (1999)]. This theory is tested on simple, few-atom systems in both the classical and quantum regimes for which highly accurate Monte Carlo data can be obtained. By incorporating quantum anharmonic corrections to the partition functions and respective weights of the isomers, we show that the superposition method can correctly describe the finite-temperature spectroscopic properties of CaAr_n systems. The use of the absorption spectrum as a possible probe of isomerization or phase changes in the argon cluster is discussed at the light of finite-size effects.
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