Diabatic representation of the Ã2A1[Btilde]2B2conical intersection in NH2

We report large-scale MRD-CI calculations of the adiabatic and diabatic electronic energies, dipole and quadrupole electric moments, and first- and second-derivative vibronic couplings for the Ã2A1 and [Btilde]2B2 states of NH2 in the region of their conical intersection. The diabatic representation has been obtained by transforming the adiabatic one under the condition that a quadrupole component has equal diagonal matrix elements in the diabatic basis. The transformation removes the singularities of the vibronic terms at the intersection locus and gives a smooth and small electronic coupling and negligible vibronic terms between the diabatic states.