Manyhyphen;body perturbation theory electronic structure calculations for the methoxy radical. I. Determination of Jahnndash;Teller energy surfaces, spinndash;orbit splitting, and Zeeman effect

摘要

Manyhyphen;body perturbation theory calculations of the electronic structure are reported forC3vand Jahnndash;Teller distorted conformations of the methoxy radical CH3O. The Jahnndash;Teller distortion reduces the energy relative to the minimum energy for theC3vstructure by minus;0.64 kcal/mol. Furthermore, the dynamic Jahnndash;Teller effect reduces the calculated spinndash;orbit splitting from 78 to 37 cmminus;1. An analysis of the Jahnndash;Teller energy surface yields theemode vibrational frequencies (ngr;4= 2314, ngr;5= 1066, ngr;6= 792 cmminus;1) and Coriolis coupling coefficients (zgr;4= 0.065, zgr;5= minus;0.152, and zgr;6= 0.186) for the ground state. The orbitalgfactorg0= 0.647 was calculated and used to determine the components of thegtensor for free methoxy and matrixhyphen;trapped methoxy. For free methoxy,gpar;= 2.645 andgperp;= 0; for the matrixhyphen;trapped radical, experimental data was used to calculate the splitting 1.7 kcal/mol of the methoxy energy level caused by its site environment. This splitting quenchesgpar;to a value of 2.096.