The low-energy electronic excitations of HRgCN and HRgNC (Rg = Xe, Rn) were computed at the TDDFT level of theory, both in the gas phase and in xenon cluster. It was found that the most prominent peak in the spectra was due to the highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) transition (∼6 eV for HRgCN and ∼4.5 eV for HRgNC). Cluster confinement brought about bathochromic shifts in the spectra and better agreement with experiment for HXeCN. The effects of spin–orbit coupling (SOC) in the heavier Rn systems were investigated: for HRnCN, SOC red-shifted the HOMO–LUMO peak, while it blue-shifted the HOMO–LUMO peak for HRnNC. Geometry optimizations were carried out for the HRgCN and HRgNC systems to locate minima and transition states for dissociation and isomerization. Effects of isotopic substitution on reaction rates were predicted. A new model core potentials basis set was introduced and effectiveness of several pseudopotential basis sets was studied.

HRgCN和HRgNC（Rg = Xe，Rn）的低能电子激发是在TDDFT理论水平上计算的，无论是在气相中还是在氙气簇中。发现光谱中最突出的峰是由于最高的占据分子轨道（HOMO）到最低的未占据的分子轨道（LUMO）跃迁（HRgCN约为6 eV，HRgNC约为4.5 eV）。团簇限制导致光谱发生红移，并与HXeCN实验更好地吻合。研究了在更重的Rn系统中自旋轨道耦合（SOC）的影响：对于HRnCN，SOC对HRnNC的HOMO-LUMO峰进行红移，而对HRnNC的HOMO-LUMO峰进行蓝移。对HRgCN和HRgNC系统进行了几何优化，以定位最小和过渡状态以进行解离和异构化。预测了同位素取代对反应速率的影响。介绍了一种新的模型核心势能基础集，并研究了几种伪势能基础集的有效性。