National and Kapodistrian University of Athens, Department of Chemistry, Laboratory of Physical Chemistry, Panepistimiopolis, Athens 15771, Greece.
J Chem Phys. 2012 Jul 21;137(3):034303. doi: 10.1063/1.4733983.
We present a theoretical study on the potential energy surface and vibrational bound states of the E electronic excited state of the HeI(2) van der Waals system. The interaction energies are computed using accurate ab initio methods and large basis sets. Relativistic small-core effective core potentials in conjunction with a quintuple-zeta quality basis set are employed for the heavy iodine atoms in multireference configuration interaction calculations for the (3)A' and (3)A" states. For the representation of the potential energy surface we used a general interpolation technique for constructing potential surfaces from ab initio data based on the reproducing kernel Hilbert space method. The surface presents global and local minima for T-shaped configurations with well-depths of 33.2 and 4.6 cm(-1), respectively. Vibrational energies and states are computed through variational quantum mechanical calculations. We found that the binding energy of the HeI(2)(E) T-shaped isomer is 16.85 cm(-1), in excellent agreement with recent experimental measurements. In lieu of more experimental data we also report our predictions on higher vibrational levels and we analyze the influence of the underlying surface on them. This is the first attempt to represent the potential surface of such a highly excited electronic state of a van der Waals complex, and it demonstrates the capability of the ab initio technology to provide accurate results for carrying out reliable studies to model experimental data.
我们对 HeI(2)范德华体系 E 电子激发态的势能面和振动束缚态进行了理论研究。使用精确的从头计算方法和大基组计算了相互作用能。对于 (3)A' 和 (3)A" 态的多参考组态相互作用计算，使用相对论小核有效核芯势与 quintuple-zeta 质量基组处理重碘原子。为了表示势能面，我们使用了基于再生核希尔伯特空间方法的从头算数据构建势能面的通用插值技术。表面呈现出 T 形构型的全局和局部最小值，其深度分别为 33.2 和 4.6 cm(-1)。通过变分量子力学计算计算振动能和态。我们发现 HeI(2)(E) T 形异构体的结合能为 16.85 cm(-1)，与最近的实验测量值非常吻合。鉴于没有更多的实验数据，我们还报告了对更高振动能级的预测，并分析了基础表面对它们的影响。这是首次尝试表示如此高激发的范德华复合物的电子态的势能面，它展示了从头计算技术提供准确结果的能力，可用于进行可靠的研究来模拟实验数据。
