On the R2PI spectrum of AgNH3: a theoretical study of the quasidegeneracy of the first excited states

The electronic ground state and the three first excited states of AgNH3 have been investigated theoretically. At the ab initio CASPT2 level, there is a quasi-degeneracy of the C3v minima of the 2A1 and 2E excited states (De=1.38 and 1.40 eV, respectively). While the 2E state displays a clear Ag(5pπ)+NH3 character, the nature of the 2A1 is more subtle, with both charge transfer and Rydberg characters. Semi-empirical introduction of the spin–orbit coupling enables the interpretation of a few features of the intricated R2PI spectrum.