Mignolet Benoît, Johansson J Olof, Campbell Eleanor E B, Remacle Françoise
Department of Chemistry, B6c, University of Liège, B4000 Liège (Belgium).
Chemphyschem. 2013 Oct 7;14(14):3332-40. doi: 10.1002/cphc.201300585. Epub 2013 Aug 8.
Super-atom molecular orbitals (SAMOs) are diffuse hydrogen-like orbitals defined by the shallow potential at the centre of hollow molecules such as fullerenes. The SAMO excited states differ from the Rydberg states by the significant electronic density present inside the carbon cage. We provide a detailed computational study of SAMO and Rydberg states and an experimental characterization of SAMO excited electronic states for gas-phase C(60) molecules by photoelectron spectroscopy. A large band of 500 excited states was computed using time-dependent density functional theory. We show that due to their diffuse character, the photoionization widths of the SAMO and Rydberg states are orders of magnitude larger than those of the isoenergetic non-SAMO excited states. Moreover, in the range of kinetic energies experimentally measured, only the SAMO states photoionize significantly on the timescale of the femtosecond laser experiments. Single photon ionization of the SAMO states dominates the photoelectron spectrum for relatively low laser intensities. The computed photoelectron spectra and photoelectron angular distributions are in good agreement with the experimental results.
超原子分子轨道（SAMOs）是由富勒烯等空心分子中心的浅势定义的类氢弥散轨道。SAMO激发态与里德堡态的不同之处在于碳笼内部存在显著的电子密度。我们通过光电子能谱对气相C(60)分子的SAMO和里德堡态进行了详细的计算研究，并对SAMO激发电子态进行了实验表征。使用含时密度泛函理论计算了500个激发态的大能带。我们表明，由于其弥散特性，SAMO和里德堡态的光电离宽度比等能量的非SAMO激发态大几个数量级。此外，在实验测量的动能范围内，只有SAMO态在飞秒激光实验的时间尺度上有显著的光电离。对于相对较低的激光强度，SAMO态的单光子电离主导了光电子能谱。计算得到的光电子能谱和光电子角分布与实验结果吻合良好。
