The Coupling Effects Of Electronic States For MgO And CN

The spectral radiation parameters of the MgO and CN molecules play an important role in radiation field simulations,astronomical surveys and the evolution of interstellar dust.Since experimental measurements only yield spectral parameters between the ground and low-lying excited states of the molecule,theoretical calculations become an important research tool in order to obtain more comprehensive spectral data.As one of the most important spectral parameters,the absorption cross section plays an important role in solving problems of radiation absorption,scattering and transmission.Further consideration of the effect of coupling effects between electronic states on absorption cross sections can provide an important guarantee for the accuracy of absorption cross sections,which is of great significance for practical engineering applications.In this thesis,based on ab initio method,a theoretical study of the electronic structure of MgO and CN molecules was carried out,aiming to obtain the absorption cross section for the bound-free transition process of MgO and the bound-bound transition process of CN,and by introducing the highly excited electronic states and coupling effect,more comprehensive and accurate absorption cross section was calculated for practical engineering applications.This paper provided a more reliable theoretical reference for practical engineering applications.The main work of this paper is as follows:(1)From the microstructure of MgO and CN molecules,the electronic structures of MgO and CN have been accurately calculated using quantum chemical calculations.The potential energy curves,dipole moment curves and coupling curves of the ground,low and highly excited states of MgO and CN molecules were calculated with aug-ccpVQZ and aug-cc-pwCV5Z-DK basis sets,respectively.The results show that there is strong coupling between the 1Π state of MgO molecules and between the high excited states of CN molecules.(2)Based on the coupled-channel theory,the predissociation process of MgO molecules has been studied.In this paper,a non-adiabatic potential energy curve was constructed,the interaction matrix of the MgO molecule for the calculation of predissociation process was established,the absorption cross section of the MgO molecule predissociation through the 1Π state was calculated,and the spin-orbit coupling effect was found to have a significant influence on the pre-dissociation cross section in the 140～200 nm range.(3)In the thesis,the absorption cross section of the CN molecule bound-bound transition process was calculated by considering spin-orbit coupling,orbital angular momentum coupling and non-adiabatic effects,and the influence of non-adiabatic effects on the absorption cross section was analyzed.In addition,the absorption cross section at T=1000 K was calculated based on Gaussian lines,and the absorption cross section at T=2000 K was calculated based on Lorentzian lines,and it was found that the coupling effect has an effect on the absorption cross section over the entire range of wave numbers calculated.(4)This thesis took the X ~2∑~+ X ~2∑~+and X ~2∑~+-A 2 Π transition processes for example and presented the data of absorption cross section with Lorentzian lines at T=300 K,1000 K.3000 K and 8000 K,respectively to provide a theoretical reference for practical applications.