  Birch reduction is a time-proven way to hydrogenate aromatic hydrocarbons
(such as benzene), which relies on the reducing power of electrons released
from alkali metals into liquid ammonia. We have succeeded to characterize the
key intermediates of the Birch reduction process - the solvated electron and
dielectron and the benzene radical anion - using cyclic voltammetry and
photoelectron spectroscopy, aided by electronic structure calculations. In this
way, we not only quantify the electron binding energies of these species, which
are decisive for the mechanism of the reaction but also use Birch reduction as
a case study to directly connect the two seemingly unrelated experimental
techniques.
