Basically, I'm asking about loosely-bound electrons, e.g. everyday static electricity. Can their combined wavefunction evolve to a low-energy state "at once", so that they emit a single high-frequency photon, rather than multiple photons of energies suggested by the potential difference? If not, what is the deeper theoretical reason for it? How does it differ from the collective excitation of a nucleus? As a 3rd (final) year undergrad this question hasn't occurred to me. I've taken introductory courses in QM, Subatomic, Statistical and Atomic-Molecular physics (exam on Monday actually). I have not taken courses in Solid State Physics (that's next term) nor in Lagrangian/Hamiltonian mechanics (that's my next course). Thanks.