Scientists experimentally showed that the change in properties of the solution of alkali metals in ammonia from electrolytic to metal gradually. In the spectra of x-ray photoelectron spectroscopy of solutions of various concentrations, the authors found that with increasing the content of metal sulfatirovannah peak of the electron splits into peaks at the Fermi level and plasmon, indicating the occurrence of metallic properties. The results of a study published in Science.
Liquid ammonia has the unusual property to solutionate electrons, forming stable solutions of alkali metals. The color of the solution depends on the amount of dissolved metal that releases electrons: if the electron is small, the solution is bright blue, and if a lot, then bronze. The details of such a transition, which is also accompanied by a sharp increase in the properties of the electron conductivity of the solution, still remained a mystery.
Batters Tillman (Tillmann Buttersack) with colleagues from Institute of organic chemistry and biochemistry Czech Academy of Sciences were able to accurately observe the change in energy with increasing electron concentration in ammonia using x-ray photoelectron spectroscopy. Soft x-ray synchrotron radiation knocked electrons out of the sample and their kinetic energy, the researchers judged about the energy States of the system. For analysis by this method requires a low pressure. Given the relatively high volatility of ammonia, is able to evaporate and increase the pressure, the authors were irradiated Metrostroi a width of about one hundred microns ammonia solutions of lithium, sodium or potassium at various concentrations.
Comparing the obtained spectra with theoretical calculations, the authors found that at low concentrations of metal, each electron sulfatirovaniu was surrounded by 10-12 molecules of ammonia, occupying a region with a diameter of about eight angstroms. The solution absorbs light in the red part of the visible spectrum, so it was dark blue. The increase in metal content resulted in the release of more electrons, which are formed pairs within the same solvent shell. At even higher concentrations the energy levels are degenerated and the solution behaved as a metallic conductor. Moreover, the metallic properties began to emerge even before the sample was visually bronze color.