ELECTRONIC SPECTROSCOPY OF Li(NH$_{3}$)$_{4}$

Author Institution: Department of Chemistry, University of Leicester, Leicester, LE1 7RH, United KingdomLi(NH$_{3}$)$_{4}$ has been proposed as a key entity in lithium-ammonia solutions, but its spectral signature has so far proved impossible to distinguish from other species in these solutions. Here we present the first electronic spectrum of Li(NH$_{3}$)$_{4}$ in the gas phase in an effort to understand the electronic structure of this important cluster. This spectrum was recorded using mass-selective depletion spectroscopy. Strong absorption is observed in the near-infrared and the band system is assigned to the \textit{\~{A}}$^{2}$T$_{2}$ - \textit{\~{X}}$^{2}$A$_{1}$ transition in a nominally tetrahedral complex. However, an extensive vibrational progression in a low frequency bending vibration is indicative of a substantial Jahn-Teller effect in the excited electronic state. Our observations confirm a recent theoretical prediction that the electronic spectrum of Li(NH$_{3}$)$_{4}$ will strongly overlap with the spectrum of the solvated electron in liquid ammonia