Potential energy curves for the dissociation of the Rydberg NH4 radical into (NH2+H2)

Abstract

Potential energy curves of the ground and excited states for the dissociation of the Rydberg NH4 radical into (NH2+H2) have been calculated using ab initio Hartree–Fock and singly and doubly excited configuration interaction methods with a large basis set including Rydberg basis functions. The ground potential curve (2A1) of the (NH4+)(e−)3s radical adiabatically correlates to the [NH2*(Ã 2A1)+H2(X̃ 1Σg+)] asymptote, while the first excited state (2T2) of (NH4+)(e−)3p correlates to [NH2(X̃ 2B1)+H2(X̃ 1Σg+)]. Two diabatic valence curves emerging from the [NH2*(Ã 2A1)+H2(X̃ 1Σg+)] and [NH2(X̃ 2B1)+H2(X̃ 1Σg+)] asymptotes are repulsively represented, while two diabatic curves from [NH2+(Ã 1A1)+H2−(X̃ 2Σu+)] and [NH2+(X̃ 3B1)+H2−(X̃2 Σu+)] are attractively represented. At shorter than R(NH)≃2.0 Å, the avoided curve crossings between the dissociative diabatic states of the [(NH4+)(e−)Rydberg] radical and the repulsive diabatic states emerging from the antibonding interactions of the [NH2+H2(X̃ 1Σg+)] asymptote are found mainly. While, at larger than R(NH)≃2.0 Å, the avoided curve crossings between the repulsive diabatic states emerging from H2 and the Rydberg states of NH2 and the attractive diabatic states from [NH2+(Ã 1A1)+H2−(X̃ 2Σu+)] and [NH2+(X̃ 3B1)+H2−(X̃ 2Σu+)] are found.