New diabatic potential energy surfaces of the NaH2 system and dynamics studies for the Na(3p)\u2009+\u2009H2\u2009\u2192\u2009NaH\u2009+\u2009H reaction

Shufen Wang,Zijiang Yang,Maodu Chen,Jiuchuang Yuan

doi:10.1038/s41598-018-35987-z

Abstract

The Na(3p) + H2(X1Σg+) → NaH(X1Σ+) + H(2S) reaction plays an important role in the field of diabatic reaction dynamics. A set of new diabatic potential energy surfaces (PESs) of the NaH2 system are structured, which include the diabatic coupling between the lowest two adiabatic states. The electronic structure calculations are performed on the multi-reference configuration interaction level with the cc-pwCVQZ and aug-cc-PVQZ basis sets for Na and H atoms. 32402 geometries are chosen to construct the diabatic data by a unitary transformation based on the molecular property method. The diabatic matrix elements of {{boldsymbol{V}}}_{{bf{11}}}^{{boldsymbol{d}}}, {{boldsymbol{V}}}_{{bf{22}}}^{{boldsymbol{d}}} and {{boldsymbol{V}}}_{{bf{12}}}^{{boldsymbol{d}}} ({{boldsymbol{V}}}_{{bf{21}}}^{{boldsymbol{d}}}) are fitted by the artificial neural network model. The spectroscopic constants of diatoms obtained from the present PESs are consistent with the experimental data. The topographical and intersection characteristics of the {{boldsymbol{V}}}_{{bf{11}}}^{{boldsymbol{d}}} and {{boldsymbol{V}}}_{{bf{22}}}^{{boldsymbol{d}}} surfaces are discussed. Based on the new PESs, the time-dependent quantum wave packet calculations are carried out to study the reaction mechanism of the title reaction in detail.

Highlights

The interactions between electronically excited alkali atoms and hydrogen molecule, including both no-reactive quenching and chemical reactions, have become an interesting topic due to the special advantage for understanding diabatic processes
A set of new global potential energy surfaces (PESs) for the NaH2 system are constructed in the diabatic representation, which are correlated with the adiabatic 1 A′state and 2 A′state
The diabatic matrix elements are generated by the transformation of ab initio data based on the molecular property method

Summary

Introduction

The interactions between electronically excited alkali atoms and hydrogen molecule, including both no-reactive quenching and chemical reactions, have become an interesting topic due to the special advantage for understanding diabatic processes. Motzkus et al.[20] applied three different nonlinear optical techniques, including coherent anti-Stokes Raman scattering (CARS), resonance-enhanced CARS, and degenerate four-wave mixing, to compare the Na(4p) + H2 and Na(3p) + H2 reaction processes This experiment showed the formation of NaH via the Na(3p) + H2 reaction follows a two-step mechanism, which is opposite to the direct reaction of Na(4p) + H2. In 1982, Donald et al.[28] calculated the lowest three PESs and diabatic coupling for the Na(3p) + H2 quenching process by using the diatomics-in-molecules (DIM) method They used a new parametrization for the diabatic potential energy curves of NaH29 to optimize the preceding PESs, which are only suitable for studying the non-reactive quenching of the Na(3p) + H2. The time-dependent wave packet (TDWP) calculations are carried out on the new diabatic PESs to obtain the quantum dynamics information of the title reaction

Methods

Results

Conclusion