Theoretical Investigations On Spectroscopoc Properties Of Loy-lying Electronic States Of CN Radical And Ncl~+ Cation

Spectral analysis is one of the effective methods for researchers to explore the structure and characteristics of materials.It is to identify the components of substances and determine their chemical composition and relative content by analyzing their absorption,emission and fluorescence spectrum.Molecular spectroscopy is an important object of spectral analysis.Through in-depth analysis of molecular spectroscopy,various unknown molecules in stars,planets,comets and interstellar space can be detected.The free radical CN(cyanogen),which formed by carbon and nitrogen,has been found in much extraterrestrial exploration and was of irreplaceable importance in astrophysics and chemical kinetics.Applications span topics from the origin and abundances of elements,the temperature of microwave background radiations,the star formation processes,to the origin of galaxies.This radical is also significant in many laboratory processes at high temperatures such as chemical reactions,flames,and discharges.The NCl radical and its cation may play important roles in the chemistry reactions between interstellar space and upper atmosphere because of the relatively high abundances of their component elements in these environments.However,so far,the molecular structure and spectral information of CN radicals and NCl~+cations have been limited to the ground state and low-electron excited states.There are few spectral studies of high-excited states,and the transition characteristics are lack of systematic theoretical studies.Therefore,the systematic theoretical studies of CN radicals and NCl+cations have important theoretical significance and potential application value.In this paper,the potential energy curves of molecules and ions are studied.Considering the core-valence correlation and douglas-kroll hamiltonian scalar relativistic correction,the potential energy is extrapolated to the completely base set limit to improve the accuracy of the potential energy curves.Based on the PECS,this thesis spectroscopic parameters(Excitation energy Te,dissociation energy De,equilibrium nuclear spacing Re,resonance frequency?e,first and second order anharmonic vibration constants?exe and?eye,equilibrium rotation constant Be and vibration rotation coupling constant?e),transition characteristics,and vibrational levels are calculated.The transition dipole moments are computed.The Franck-Condon factors,Einstein coefficients,and radiative lifetimes of many transitions are determined.The spin-orbit coupling effects on the spectroscopic and vibrational properties are evaluated.First of all,thesis studies ten low–lying states of CN radical.These states are X~2?~+,A~2?,B~2?~+,a~4?~+,b~4?,1~4?~-,2~4?,1~4?,1~6?~+,and 1~6?.The potential energy curves are calculated using the CASSCF method,which is followed by the icMRCI approach with the Davidson correction.The transition probabilities of electric dipole transitions,Franck–Condon factors,and Einstein coefficients of emissions are calculated.The radiative lifetimes are determined for the vibrational levels of the A~2?,B~2?~+,b~4?,1~4?~-,2~4?,1~4?,and 1~6?states.The radiation lifetimes of A~2?,B~2?~+and 2~4?states are very short,and the lower vibrational levels of 1~6?,1~4?and 1~4?~-states have longer radiation lifetimes.Next,this work calculates the potential energy curves of 9?-S and 28?states of the NCl~+cation.The technique employed is the complete active space self-consistent field method,which is followed by the internally contracted multireference configuration interaction approach with the Davidson correction.The?-S states are X~2?,1~2?~+,1~4?,1~4?~+,1~4?~-,2~4?,1~4?,1~6?~+and 1~6?.The 1~4?,1~4?,1~6?~+and 1~6?states are inverted with the spin-orbit coupling effect included.The transition probabilities of electric dipole transitions,Franck–Condon factors,Einstein coefficients and radiative lifetimes of emissions are calculated.X~2?,,1~4?,and 1~4?~-states,some of these transitions have larger Einstein coefficients and smaller radiation lifetimes.1~4?and 2~4?also have some spontaneous radiation with shorter radiation lifetime.Compared with previous experimental and theoretical data,the potential energy curve,spectroscopic parameters,transition dipole moments and transition probabilities reported in this thesis are very accurate,which also provides theoretical guidance for the future detection of the existence of these electronic states and the occurrence of the transition between them.