Theoretical study of the Renner-Teller òA₁-[Xtilde]²B₁system of NH₂

Three-dimensional potential energy functions of the à 2B1-[Xtilde] 2A1 bent-bent Renner-Teller system of NH2 have been generated and used in calculations of the rovibronic energy levels (J ⩽ 9>/2) by a variational approach accounting for anharmonicity, rotation-vibration, electronic angular momenta and electron-spin coupling effects. For low values of N, the theoretical rovibronic term values up to about 20 000 cm-1 agree with available experimental data to within a few wavenumbers. For the first time, all existing rovibronic states for N = 0 and 1 are given and assigned up to 18 000 cm-1. For higher levels including stretching modes the Fermi polyads have been used in the assignments.