Some Photolysis Bromine-containing Compounds From The Mechanism And The Excited State HXY System Of Multi-reference-state Study

This paper mainly includes two parts. The first part focuses on the photodissociationmechanism of some alkyl bromides. In this part, the MS-CASPT2//CASSCF andMS-CASPT2/CASSI-SO calculations were carried out using the MOLCAS7.4quantumsoftware. The relativistic basis sets of the atomic natural orbital type, ANO/RCC, wereused for all calculations. The second part concentrates on the multireference study onsome excited states of the HXY system. In this part, the CASSCF/ANO, CASPT2/ANO,and CASPT2//CASSCF calculations were performed using the MOLCAS7.4quantumsoftware.The photodissociation of alkyl bromides （C₂H₅Br,1,2-C₂H₄Br₂,1,2-C₂H₄BrCl） hasbeen investigated by spin-orbit ab initio calculations. The vertical excitation energies ofsome excited states for these alkyl bromides were calculated. The potential energy curveswere calculated by multistate second order multiconfigurational perturbation theory inconjunction with spin-orbit interaction through complete active space state interaction（MS-CASPT2/CASSI-SO）. The origin of dissociation products Br (²P_3/2) and Br*(²P_1/2)states were discussed.Some low-lying states of the nine-valence-electron systems HXY-HYX: HBS⁺-HSB⁺,HBP-HPB, HAlN-HNAl, HAlS+-HSAl⁺, HAlO⁺-HOAl⁺and HMgO-HOMg have beenstudied by large-scale theoretical calculations using three methods CASSCF, CASPT2,and B3LYP with the contracted atomic natural orbital and cc-pVTZ basis sets. Thegeometries of all stationary points along the potential energy surfaces were optimized andthe energies were calculated. The potential energy curves of isomerization reactionsbetween HXY-HYX were calculated as a function of HXY bond angle. At the same time,we will test whether these nine-valence-electron systems HXY-HYX in accordance withthe Walsh′s rule or not.