Intramolecular vibrational relaxation from CH stretching modes in dimethylnitramine

Intramolecular vibrational energy transfer in dimethylnitramine has been studied using classical trajectories. Model harmonic and anharmonic valence force-field potential-energy surfaces with force constants adjusted to give approximately the known normal-mode frequencies were used in the study. Both the rate and mechanism for energy flow from high CH stretch and methyl group excited states were investigated. The results show that the energy transfer is rapid (within approximately 0.25 ps) and irreversible. The energy from an excited CH stretch is initially transferred to the methyl bending motion and finally to the nitro and "second" methyl groups. The dominant energy transfer path involves flow from the stretch to the bend within the excited group followed by "methyl-to-methyl" transfer.