Spectroscopic Constants And Anharmonic Force Fields Of Sulfur Compounds And CH₂OO:An Ab Inito Study

As an important part of physics,atomic and molecular physics is regarded as a bridge connecting macroscopic and microscopic worlds.Molecular spectroscopy is an important window for people to explore and understand the internal structure and properties of molecules,which is of great significance to astrophysics,plasma and laser physics.Theoretical study on molecular spectroscopy can unveil the information carried by the experimental spectra and further establish a direct connection with the microscopic properties of the system.The massive emission of sulfur compounds threatens the growth of plants and animals and even human health,affecting climate change and ozone depletion.The research on sulfur compounds is also closely related to the development of electronics industry and greenhouse gas emission reduction.The CH2OO molecule,as the simplest Criegee intermediate,plays a key role in controlling the concentration changes of hydroxyl radicals,organic acids,peroxides,nitrates and sulfates in atmospheric environment.Therefore,in recent years,the gas phase spectroscopic characterization of sulfur compounds and CH2OO molecule has attracted much attention.The core work of this paper is to calculate the spectroscopic constants and anharmonic force field of sulfur compounds and CH2OO by ab initio method.First,the equilibrium geometry of F2SO(X1A')was reported employing B3LYP,B3P86,B3PW91 and MP2 methods combining with higher-order correlation consistent cc-pVQZ,cc-pV5Z,aug-cc-pVQZ and aug-cc-pV5Z basis sets.On this basis,the spectroscopic constants and anharmonic force field of the equilibrium state were calculated using the same theoretical level.The calculated values were compared with the existing theoretical and experimental reference values,and some unmeasured spectroscopic data of F2SO,such as anharmonic constants,centrifugal distortion constants and Coriolis coupling constants are also predicted.Then,we also calculate equilibrium geometry,energy,force constants,and a set of spectroscopic constants of the four isomers of SO3(cis-OSOO,trans-OSOO,OS(=O)O and SOOO)performed with Density Functional Theory(DFT)in combination with cc-pVnZ and aug-cc-pVnZ(n=T,Q)basis sets.Subsequently,the relationship between molecular structure and spectroscopic properties of four isomers of SO3 was analyzed in detail.Finally,the B3LYP method and the CAM-B3LYP method(based on the B3LYP method using the Coulomb attenuation method and considering the long range correction)combining with 6-311++G**and the aug-cc-pVQZ basis set were used to study the vibrational spectroscopic constants and anharmonic force field of CH2OO(X1A'/A1A"/B1A').This work is a further development of the previous work and extends the theoretical study of the vibrational spectroscopic constants and anharmonic field of polyatomic molecules from the ground state to the excited state of molecules.In addition,a series of spectroscopic constants and force constants of each order of CH2OO(X1A'/A1A"/B1A')are also predicted,in the hope of providing theoretical support for future experimental studies.