Nicu Valentin Paul
Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Phys Chem Chem Phys. 2016 Aug 3;18(31):21213-25. doi: 10.1039/c6cp01283c.
Using two illustrative examples it is shown that the generalised coupled oscillator (GCO) mechanism implies that the stability of the VCD sign computed for a given normal mode is not reflected by the magnitude of the ratio ζ between the rotational strength and dipole strength of the respective mode, i.e., the VCD robustness criterium proposed by Góbi and Magyarfalvi. The performed VCD GCO analysis brings further insight into the GCO mechanism and also into the VCD robustness concept. First, it shows that the GCO mechanism can be interpreted as a VCD resonance enhancement mechanism, i.e. very large VCD signals can be observed when the interacting molecular fragments are in favourable orientation. Second, it shows that the uncertainties observed in the computed VCD signs are associated to uncertainties in the relative orientation of the coupled oscillator fragments and/or to uncertainties in the predicted nuclear displacement vectors, i.e. not uncertainties in the computed magnetic dipole transition moments as was originally assumed. Since it is able to identify such situations easily, the VCD GCO analysis can be used as a VCD robustness analysis.
通过两个示例表明，广义耦合振子（GCO）机制意味着，为给定的简正模式计算的VCD信号的稳定性，并非由相应模式的旋转强度与偶极强度之比ζ的大小反映，即并非由戈比（Góbi）和马加尔法尔维（Magyarfalvi）提出的VCD稳健性标准反映。所进行的VCD GCO分析进一步深入了解了GCO机制以及VCD稳健性概念。首先，它表明GCO机制可被解释为一种VCD共振增强机制，即当相互作用的分子片段处于有利取向时，可观察到非常大的VCD信号。其次，它表明在计算的VCD符号中观察到的不确定性与耦合振子片段的相对取向的不确定性和/或预测的核位移矢量的不确定性相关，即并非如最初所假设的那样与计算的磁偶极跃迁矩的不确定性相关。由于VCD GCO分析能够轻松识别此类情况，因此可将其用作VCD稳健性分析。
