The active state of carbon atoms is achieved in plasma at rigid energetic conditions. Proportion of particles with enough energy to activate carbon atoms is small. This work considers the result of energy input to carbon atom, which was in inert state. It was shown that subsequent excitement and recombination activated carbon atoms. Active atoms formed covalent bonds with other atoms in crystal diamond. The states of carbon atoms and its subsequent transitions to the active state were revealed. The calculations have found that carbon atoms activization energy value is equal to 17,581079 eV.