Communications: The electronic spectrum of Li (NH3)4

Abstract

Li (NH3) 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 report the first electronic spectrum of Li (NH3) 4 in the gas phase, which was recorded using mass-selective depletion spectroscopy. Strong absorption is observed in the near-infrared and the band system is assigned to the Ã2T2 - X̃2A1 transition in a nominally tetrahedral complex. However, the vibrational structure is indicative of a substantial Jahn-Teller effect in the excited electronic state. The broad and structured spectrum confirms a recent theoretical prediction that the electronic spectrum of Li (NH3) 4 will strongly overlap with the spectrum of the solvated electron in lithium-ammonia solutions. © 2010 American Institute of Physics.