State Key Laboratory of Precision Spectroscopy and Institute of Theoretical and Computational Science, East China Normal University, Shanghai 200062, China.
J Chem Phys. 2013 Aug 14;139(6):064309. doi: 10.1063/1.4817534.
In the supramolecular complex H2@C60, the lightest of molecules, H2, is encapsulated inside the most highly symmetric molecule C60. The elegance and apparent simplicity of H2@C60 conceal highly intricate quantum dynamics of the coupled translational and rotational motions of the guest molecule in a nearly spherical nanoscale cavity, which embodies some of the most fundamental concepts of quantum mechanics. Here we present the first rigorous and highly accurate quantum calculations of the inelastic neutron scattering (INS) spectra of this prototypical endohedral fullerene complex and their temperature dependence. The calculations enable complete assignment of the recently reported experimental INS spectra of H2@C60 measured at several temperatures. We also derive a new and unexpected selection rule for the INS spectroscopy of H2 in a near-spherical confinement, which explains why the INS transitions between certain translation-rotation eigenstates of H2 in C60 have zero intensity and do not appear in the spectra.
在超分子复合物 H2@C60 中，最轻的分子 H2 被封装在对称性最高的分子 C60 内部。H2@C60 的优雅和明显的简单性掩盖了客体分子在近球形纳米级腔中的耦合平动和转动运动的高度复杂的量子动力学，这体现了量子力学的一些最基本概念。在这里，我们首次对这种典型的笼状富勒烯复合物的非弹性中子散射（INS）光谱及其温度依赖性进行了严格和高度精确的量子计算。这些计算能够完全确定最近报道的在几个温度下测量的 H2@C60 的实验 INS 光谱的归属。我们还推导出了在近球形约束下对 H2 的 INS 光谱的一个新的、意想不到的选择定则，这解释了为什么在 C60 中 H2 的某些平动-转动本征态之间的 INS 跃迁的强度为零，并且不会出现在光谱中。
