REACTION BARRIER FOR THE METHYLDIAZENYL RADICAL DECOMPOSITION (CH3N2-]CH3+N-2)

The reaction of ground state ((2)A') CH3N2-->CH3+N-2 was studied using the ab initio quantum mechanical techniques, including the self-consistent field (SCF), single and double excitation configuration interaction (CISD), single and double excitation coupled cluster (CCSD), and the single, double, and perturbative triple excitation coupled cluster [CCSD(T)]. The classical barrier for the methyldiazenyl radical decomposition was predicted at the highest level of theory to be 4.5 kcal/mol and was 2.3 kcal/mol when zero-point vibrational energy corrections are included. This result is pertinent to the apparently conflicting experimental results of the Rice and Berkeley groups. The very small theoretical reaction barrier agrees with the recent experimental observation that lifetime of CH3N2 is very short, at the picosecond range.