  Angle-resolved photoemission spectra of alkali metals exhibit a puzzling,
non-dispersing peak in the apparent density of states near the Fermi energy. We
argue that the holes left behind a significant fraction of photoejected
electrons are not wavepacket-like objects used to describe excitations of an
equilibrium Fermi liquid but, instead, are relatively localized entities
resulting from a photon-induced cavitation in the electron fluid. At the same
time, these special localized holes can be thought of as vacancies in a
transient Wigner solid. The corresponding contribution to the photoemission
current is non-dispersive and is tied to the Fermi level; it exhibits certain
similarities to photoemission from localized core orbitals such as the presence
of recoil currents. Calculated spectra are consistent with experiment. We
briefly discuss the present findings in the context of quantum measurement.
