Theoretical studies of the electronic structure and spectra of low-lying states of NH₃⁺

We report on ab initio calculations of the energies and geometries of the 2A″2 ground state and the 2E and 2A′1 excited states of NH3+. The Jahn-Teller distortion of the 2E is treated in detail. By global geometry optimization we determine that the Jahn-Teller stabilization energy is between 1.2 and 1.4 eV and that the 2A″ state is the lowest energy Jahn-Teller component. We find that angular distortions provide the major contribution to the stabilization energy and that the JT distortion is a static one. Nonlinear electronic-vibrational coupling appears to be important but intermode coupling is small. Finally, we discuss the second photoelectron band of NH3 and the observed photofragmentation patterns in terms of the computed state energies and geometries. © 1983 American Institute of Physics.