The Study Of Geometric Structures And Spectroscopic Properties Of Molecules Containing Antimonide

Molecular structures and properties are the key research contents in subjects of atomic and molecular physics,theoretical chemistry,etc.Since molecular potential energy functions can fully describe the related properties of molecular systems,they have played important roles in both theoretical researches and experimental applications.BeSb is an ideal choice for radioisotope neutron sources,where neutrons can be formed through the photon-neutron reaction from the interaction between ¹²⁴Sb and Be.Combined with the thermal neutron photography and tomography,the neutron source has been developed and applied in engineering and industrial fields.However,basic structural and spectroscopic parameters of the BeSb have not been reported yet.On the contrary,several other diatomic systems that composed of the IIA and VA group elements,such as BeN,BeP,BeAs,MgAs,have been studied,and their corresponding properties have receive remarkable considerations.Therefore,in this thesis,we will focus on the physical properties of BeSb and MgSb molecules.In this paper,several electronic states of BeSb and MgSb are investigated by utilizing the MOLPRO 2015.1 package.The Murrell-Sorbie potential energy function is used to fit the calculated energy points,and the geometric structures,potential energy curves,as well as their corresponding spectroscopic constants are derived.The energy points are obtained by the state-averaged complete active space self-consistent field?SA-CASSCF?method and the multireference configuration interaction?MRCI?method with the Davidson correction?+Q?,coupled with the relativistic augmented correlation-consistent polarized core-valence quintuple-zeta basis set.The vibrational energy levels for the twelve?-S states of both BeSb and MgSb are then obtained.Furthermore,results of BeSb are also analyzed and compared with those of the Beryllium-VA group diatomic family species where data are available.Moreover,the permanent dipole moments,transition dipole moments,Einstein emission coefficients,radiative lifetimes and Franck-Condon factors for interested?-S states are derived with the aid of the LEVEL 8.0 program.Further assessments of the spin-orbit coupling effect are performed for states associated with the first two dissociation asymptotes of BeSb and MgSb.Four?-S states split into seven?states,and some of the PECs are distorted significantly through the spin-orbit coupling effect.In consideration of potential risks of manipulating beryllium-and antimony-containing species directly,the information associated with molecular structures,spectroscopic parameters as well as transition properties that provide in this thesis is anticipated to serve as guidelines for further researches of BeSb and MgSb.