Accurate Potential Energy Surfaces for the Three Lowest Electronic States of N(2D) + H2(X1∑g+) Scattering Reaction

The three lowest full three-dimensional adiabatic and three diabatic global potential energy surfaces are reported for the title system. The accurate ab initio method (MCSCF/MRCI) with larger basis sets (aug-cc-pVQZ) is used to reduce the adiabatic potential energies, and the global adiabatic potential energy surfaces are deduced by a three-dimensional B-spline fitting method. The conical intersections and the mixing angles between the lowest three adiabatic potential energy surfaces are precisely studied. The most possible nonadiabatic reaction pathways are predicted, i.e., N­(2D) + H2(X1∑g+) → NH2(22A′) → CI (12A′–22A′) → NH2(12A′) → CI (12A″–12A′) → NH2(12A″) → NH­(X3∑–) + H­(2S). The products of the first excited state (NH­(a1Δ) + H­(2S)) and the second excited state (NH­(b1∑g+) + H­(2S)) can be generated in these nonadiabatic reaction pathways too.本文针对标题所述体系，报道了3个最低阶全维绝热全局势能面（adiabatic global potential energy surface）与3个 diabatic 全局势能面（diabatic global potential energy surfaces）。采用配备更大基组aug-cc-pVQZ的高精度从头算方法（ab initio method，MCSCF/MRCI）计算绝热势能能值，并通过三维B样条拟合方法推导出全局绝热势能面。本文对最低3个绝热势能面间的锥形交叉点（conical intersections）与混合角开展了精准研究，并预测了最具可行性的非绝热反应路径（nonadiabatic reaction pathways）：即N(2D) + H2(X1∑g+) → NH2(22A′) → 锥形交叉（CI，12A′–22A′） → NH2(12A′) → 锥形交叉（CI，12A″–12A′） → NH2(12A″) → NH(X3∑–) + H(2S)。上述非绝热反应路径亦可生成第一激发态产物NH(a1Δ) + H(2S)与第二激发态产物NH(b1∑g+) + H(2S)。