Metallic Li(NH3)4 photographed in liquid nitrogen in the open lab. This ultra-light bronze metal even floats!
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When alkali metals are dissolved in anhydrous liquid ammonia they give up their outer-shell electrons to the solvent producing solvated electrons and metal ions. At low metal concentrations, the solutions are electrolytic in nature and deep blue in colour. As the concentration is increased, the solutions transform to a fine bronze colour with metallic lustre.
Lithium-ammonia solutions are unique amongst the alkali metal systems in that they form a highly conductive crystalline compound Li(NH3)4 at low temperature.
The metallic nature of these systems makes recording of vibrational spectra particularly challenging! Our inelastic neutron scattering measurements on Tosca represent the first look into the vibrational modes of this fascinating metallic material, revealing unique insights into the vibrational characteristics of this molecular system, the lightest metal known.
MTJ Lodge, PP Edwards (Oxford University), WIF David, AJ Ramirez-Cuesta (ISIS)
Research date: January 2010
Contact: Prof PP Edwards, firstname.lastname@example.org
Further reading: E Zurek et al., Ang Chem Int Ed 48 (2009) 8198
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