Experimental studies of the electronic structure of excess electrons in liquids – archetypal quantum solutes – have been largely restricted to very dilute
electron concentrations. Here, we overcome 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 eV,
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. In combination 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.