Potential Energy Function And Vibrational Energy Levels For The Ground State X～3∑_g～- And The Excited State B～1∑_g～+ Of O₂ Molecule

In this paper, we have studied the molecular structure and potential energyfunction and the vibrational energy level for the ground state X³ sum from g=- and the excitedstate b¹ sum from g=+ of O₂ molecule.Firstly, We have derived the reasonable dissociation limits for the O₂ molecularbased on the general principle of Atomic and Molecular Reaction and the grouptheoretical derivation of molecular electronic states.Secondly, The equilibrium geometries and harmonic frequencies of the excitedstate b¹ sum from g=+ of O₂ molecule have been calculated by using the methods ofQCISD(T),CISD,CID and HF based on set 6-311+G^*, Comparing theabove-mentioned four methods,the conclusion is gained that the QCISD(T) is themost suitable method;The whole potential curve for the state is further scanned byusing QCISD(T)/6-311+G^* method, PG function is fitted by least-squares, thengained the potential function of O₂ molecule;Comparing the scanned curve,the fittingcurve and the experimental curve,which are in good agreement, Then we get theparts of the vibrated energy level of the excited state b¹ sum from g=+ of O₂ molecule by usingthe Spectrum Data, comparing the vibrated energy level with the experimentallevel,which are in good agreement.Lastly, The equilibrium geometries and harmonic frequencies of the ground stateX³ sum from g=- of O₂ molecule have been calculated by using the methods of QCISD(T)based on sets of 6-311++G^**,6-311+G^* and 6-311G^*, the QCISD(T)/6-311++G^** isthe most suitable method, The whole potential curve for this state is further scannedby using this method,we gained the Spectrum Data by using the least-squares.Comparing the scanned curve,the fitting curve and the experimental curve,which arein good agreement, Then using the Spectrum Data we get the parts of the vibratedenergy level of the ground state X³ sum from g=- of O₂ molecule,comparing the vibratedenergy level with the experimental level,finding that they are in good agreement.