Solvation of Sodium Dimer in Ammonia Clusters: Photoelectron Spectroscopy and ab Initio Study of Na2-(NH3)n

Abstract

Photoelectron spectra (PESs) of Na2-(NH3)n (n = 0−5) are investigated to explore the solvation of sodium dimer in small ammonia clusters. We also calculate the structures and energetics of Na2-(NH3)n (n = 0−3) as well as the vertical detachment energies (VDEs) associated with the transitions to various neutral states for n up to 2 by using an ab initio MO method. The PES of Na2-(NH3) exhibits five bands at the VDE of 0.41, 1.36, 1.86, 2.11, and 2.40 eV. These bands are reproduced theoretically with a reasonable accuracy and assigned to the transitions from the anion ground state, 12Σu+(X-), to the neutral ground, 11Σg+(X), and low-lying four excited states derived from the 13Σu+(a), 13Πu(b), 11Σu+(A), and 13Σg+ states of Na2, respectively. The VDEs to the neutral ground state for all clusters examined are found to be slightly smaller than or equal to that of Na2(11Σg+), while that to the first excited state derived from Na2(13Σu+) increases gradually for n = 4 and 5. In addition, the higher-energy transit...