The optical absorbance property of carbene-N 2 adduct along the reaction path is stud- It is observed that the reactants and product have no significant absorbance in the visible region. However, due to the advancement of the reaction, a peak within the visible region appears at 474 nm with very low absorbance intensity. A blue shift of this peak is observed This study posits that though the reactants and products of a reaction are inactive in a particular region of electromagnetic radiation, they may exhibit activity in that zone during a chemical reaction. This type of optical absorbance behavior may be termed the Evanescent optical absorbance phenomenon of a reaction. If the reaction is irradiated with electromagnetic radiation where the evanescent optical activity is observed, a new type of emission property may be accomplished. kinds of transitions. HOMO to LUMO transition is responsible for the initial absorbance which occurs along the reactant path and LUMO to HOMO transition is observed along the product path. These satisfy our previous observations that donation and back donation of electrons occur before and after the crossing of the transition state. It also attests to the carbene -N 2 binding mechanism proposed in section 3.2.2. It is also concluded that bonding requires lower energy than back bonding which is obvious.