The ground and excited state potential energy surfaces of nitromethane related to its dissociation dynamics after excitation at 193 nm

摘要

The relevant low-lying singlet and triplet potential energy surfaces in the photolysis of nitromethane have been studied by using the multistte extension of the multiconfigurational second-order perturbation theory in conjunction with large atomic natural orbital-type basis sets.The proposed mechanism for the photolytic decomposition of CH_3NO_2 provides a consistent and reinterpreted picture of the avaiable experimental results.Two reaction paths are found in the photolysis of nitromethane after excitation at 193 nm:(1) major Channel,CH_3NO_2(1A')+hv(193nm)->CH_3NO_2(2Ain)->CH_3(1Aft_1)+NO_2(1~2B_1)->CH_3(1Aft_1)+NO_2(1~2A_1)->CH_3(1Aft_1)+NO_2(1~2B_1)->CH_3(1A'_1)+NO_2(1~2A)1)->CH_3(1Ain)+NO(A~2SIGMA~+)_alpha O(~3P)+BATEO(~1D).(2) Minor Channel,CH_3NO_2(1A')+hv(193nm)->CH_3NO_2(2Ain)->CH_3(1A'_1)+NO_2(1~2A_2)->CH_3(1A'_1)+NO(X~2II)+alphaO(~3P) +BETAO(1D),being alpha dn beta fractional numbers.No ionic specties are found in any dissociation path.Additionally,the respective low-lying Rydberg statesof nitromethane and nitrogen dioxide have been studied too.