Does Sub-Barrier Bremsstrahlung in alpha-decay of 210Po Exist?
  A quantum mechanical model for the description of the alpha-decay of heavy nuclei with accompanying photons emission is presented. The model is based on a quantum mechanical one-particle model of alpha-decay through a decay barrier. The bremsstrahlung spectrum calculation employs multipole expansion of the vector potential of the Coulomb field of the daughter nucleus and takes into account the dependence on the angle between the directions of the alpha-particle propagation and the photon emission. Spectra of 210Po are obtained for the angles 25 and 90, and the best agreement with the experimental data in the 90 case in a comparison with other existing models is achieved.   From the angular analysis, the model gives monotonic behavior of the bremsstrahlung spectrum for any value of the angle. We find that sub-barrier photon emission (i. e. bremsstrahlung photon emission during alpha-particle tunneling through decay barrier) exists but gives a small contribution to the total bremsstrahlung spectrum. 
Sergei P. Maydanyuk, Vladislav S. Olkhovsky (Institute for Nuclear   Research, Kiev, Ukraine)