  We present the first fully quantum mechanical calculation of photon radiation
accompanying charged particle decay from a barrier resonance. The soft-photon
limit agrees with the classical results, but differences appear at
next-to-leading-order. Under the conditions of alpha-decay of heavy nuclei, the
main contribution to the photon emission stems from Coulomb acceleration and
may be computed analytically. We find only a small contribution from the
tunneling wave function under the barrier.
