Mechanisms for N 3 formation in radiated solid nitrogen: Computational predictions including excited electronic states

A computational investigation of the azide radical formation from two N 2 molecules was carried out employing the CASSCF and MRCI electronic structure methods. Potential energy curves were built considering various electronic excited states along proposed reaction coordinates. Reaction paths with C 2v and C s symmetries were considered and energy barriers were estimated, as well as intersections between key electronic states were found. A possible reaction mechanism is suggested involving a nitrogen atom abstraction to produce linear N 3 . The distinction between N 3 formed by UV radiated ices and other sources of energy is presented and rationalized. Among other results, we predict that the N 3 radical can react barrierlessly with N( 2 D) atoms, yielding N 2 + N 2 products.