Understanding photolysis of CH3ONO2 with on-the-fly nonadiabatic dynamics simulation at the ADC(2) level

Abstract

The nonadiabatic dynamics of methyl nitrate (CH3ONO2) is studied with the on-the-fly trajectory surface hopping dynamics at the ADC(2) level. The results confirmed the existence of the ultrafast nonadiabatic decay to the electronic ground state. When the dynamics starts from S1 and S2, the photoproducts are CH3O+NO2, consistent with previous results obtained from the experimental studies and theoretical dynamics simulations at more accurate XMS-CASPT2 level. The photolysis products are CH3O+NO2 at the ADC(2) level when the dynamics starts from S3, while different photolysis products were obtained in previous experimental and theoretical works. These results demonstrate that the ADC(2) method may still be useful for treating the photolysis mechanism of CH3ONO2 at the long-wavelength UV excitation, while great caution should be paid due to its inaccurate performance in the description of the photolysis dynamics at the short-wavelength UV excitation. This gives valuable information to access the accuracy when other alkyl nitrates are treated at the ADC(2) level.