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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Absorption Spectroscopy, a Tool for Probing Local Structures and the Onset of Large-Amplitude Motions in Small KArn Clusters at Increasing Temperatures
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Absorption Spectroscopy, a Tool for Probing Local Structures and the Onset of Large-Amplitude Motions in Small KArn Clusters at Increasing Temperatures

机译：吸收光谱法，一种探测小型结构的工具，以及在高温下在小型卡尔恩星团中发生大振幅运动的工具

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摘要

Photoabsorption spectra of KArn (n = 1-10) are simulated at temperatures ranging between 5 and 25 K. The calculations associate a Monte Carlo (MC) method to sample cluster geometries at temperature T, with a one-electron ab initio model to calculate the ground-state and excited-state energies of the cluster. The latter model replaces the K+ core electrons and all the electrons of the Ar atoms by appropriate pseudopotentials, complemented by core polarization potentials. It also provides the necessary oscillator strengths to simulate the spectra. Global optimization by basin-hopping is used in combination with MC simulation at low temperature (5 K) to identify the most stable isomer and remarkable isomers of ground-state KArn clusters, which are stable with respect to deformations of the order of those expected with Zero Point Energy motions. The absorption spectra calculated for each of these isomers at 5 K suggest that absorption spectroscopy can probe sensitively the local environment of K atom: surface location of K with respect to a close-packed Ar moiety, number of Ar atom in close vicinity, and local symmetry about K. Simulation at increasing temperatures, up to the evaporation limit of K out of the cluster, shows the onset of large amplitude motions above 20 K, when the K atom experiences a variety of local environments.
机译：在5至25 K的温度范围内模拟了KArn（n = 1-10）的光吸收光谱。计算将Monte Carlo（MC）方法与温度T下的簇几何形状样本进行了关联，并使用了一个单电子从头算模型进行计算团簇的基态和激发态能量。后一种模型通过适当的伪电势补充了K +核心电子和Ar原子的所有电子，并辅以核心极化电势。它还提供了必要的振荡器强度来模拟光谱。通过盆地跳跃的全局优化与低温（5 K）下的MC模拟结合使用，以识别基态KArn团簇的最稳定的异构体和显着的异构体，这些异构体的变形量约为预期的稳定值。零点能量运动。计算出的这些异构体在5 K时的吸收光谱表明，吸收光谱法可以灵敏地探测K原子的局部环境：K相对于紧密堆积的Ar部分的表面位置，紧邻的Ar原子数和局部关于K的对称性。在不断增加的温度下进行的模拟（直到K从团簇中蒸发出来的极限）表明，当K原子经历各种局部环境时，会出现20 K以上的大振幅运动。

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