Buttersack, T.; Mason, P.E.; McMullen, R.S.; Schewe, H. C.; Martinek, T.; Brezina, K.; Crhan, M.; Gomez, A.; Hein, D.; Wartner, G.; Seidel, R.; Ali, H.; Thürmer, S.; Marsalek, O.; Winter, B.; Bradforth, S.E.; Jungwirth, P.: Photoelectron spectra of alkali metal–ammonia microjets: From blue electrolyte to bronze metal. Science 368 (2020), p. 1086-1091
10.1126/science.aaz7607
Open Access Version
Abstract:
Experimental studies of the electronic structure of excess electrons in liquids—archetypal quantum solutes—have been largely restricted to very dilute electron concentrations. We overcame this limitation by applying soft x-ray photoelectron spectroscopy to characterize excess electrons originating from steadily increasing amounts of alkali metals dissolved in refrigerated liquid ammonia microjets. As concentration rises, a narrow peak at ~2 electron volts, corresponding to vertical photodetachment of localized solvated electrons and dielectrons, transforms continuously into a band with a sharp Fermi edge accompanied by a plasmon peak, characteristic of delocalized metallic electrons. Through our experimental approach combined with ab initio calculations of localized electrons and dielectrons, we obtain a clear picture of the energetics and density of states of the ammoniated electrons over the gradual transition from dilute blue electrolytes to concentrated bronze metallic solutions.