Theoretical study of the rearrangement of Ag(NH3)2 after electronic excitation. Comparison with Na(NH3)2

Ab initio CASPT2 calculations show that the Ag(NH3)2 cluster displays two isomers (surface and interior), both in its ground and first excited states. In the ground state the surface structure is slightly preferred, whereas in the three first (quasidegenerate) excited states the interior structure is strongly preferred, like in the ionic cluster. This feature explains the fall of the ion signal observed (on the ns scale) in the R2PI spectrum: the signal vanishes as the excited cluster passes the isomerisation barrier. Comparison with the Na(NH3)2 system is made.