In this work, we have combined the multi-reference double-excitation configuration interaction method, developed by Buenker and Peyerimhoff (1974 Theor. Chim. Acta 35 33), with molecular orbitals optimized with a multi-configurational self-consistent-field approach. Using the example of the water molecule, we show that such a combined technique lowers the computational costs while improving the overall accuracy, especially for highly excited states. With this new approach, we have computed the full-dimensional potential energy surfaces (PESs) of water molecule up to the states. Furthermore, using these PESs we study the photodissociation dynamics of water triggered with short wavelength photons, which have been investigated in recent free electron laser experiments. Our results indicate new and efficient fragmentation pathways. This work paves the way to the study of reaction dynamics of polyatomic molecules in high-lying electronic states.

在这项工作中，我们将 Buenker 和 Peyerimhoff (1974 Theor . Chim. Acta 35 33)开发的多参考双激发构型相互作用方法与使用多构型自洽场方法优化的分子轨道相结合。使用水分子的例子，我们表明这种组合技术降低了计算成本，同时提高了整体精度，特别是对于高激发态。使用这种新方法，我们计算了水分子的全维势能面 (PES)，直至状态。此外，我们使用这些 PES 研究了由短波长光子触发的水的光解动力学，这已在最近的自由电子激光实验中进行了研究。我们的结果表明新的和有效的碎片途径。这项工作为研究处于高电子态的多原子分子的反应动力学铺平了道路。