Communications: The electronic spectrum of Li(NH3)4

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 (A) over tilde T-2(2)-(X) over tilde (2)A(1) 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. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3396023]