Photodissociation mechanism of MgN 2+ ion-molecule complex. An ab initio MO study

Abstract

Potential energy curves (PECs) for the dissociation of the MgN 2 + complex have been calculated by means of the ab initio MO method for the ground (X 2∑) and low-lying excited ( 2 Π and 2 2∑) states. The PECs for the ground and the first excited states were bound with respect to both dissociation limits, Mg +( 2S) + N 2 and Mg +( 2P) + N 2 , respectively. A linear structure was obtained as the most stable form of the complex on the ground state PEC. The CI calculations showed that the first excitation energy ( 2 Π ← X 2∑) was red-shifted relative to that for free Mg +( 1P ← 2 S ) transition owing to the formation of an excited state complex with a π interaction between Mg +(3p) and N 2( π NN ). The PEC for the second excited state (2 2∑) has a strongly repulsive shape because of a σ ∗ interaction between Mg +(3p) and N 2(nσ). The photodissociation and NN bond activation mechanisms of the MgN 2 + complex are discussed on the basis of the PEC characteristics.