Tunneling times and bremsstrahlung in alpha decay
  A semi-classical model based on quantum time concepts is presented for the evaluation of bremsstrahlung emission probabilities in alpha decay of nuclei. The contribution to the bremsstrahlung emission from the different regions in tunneling is investigated using realistic double folded nuclear and Coulomb potentials. Within this model, the contribution from the radiation emitted in front of the barrier before tunneling is much larger than that while leaving the barrier. A comparison with the data on $^{210}$Po shows that the results are sensitive to the nuclear potential and the rectangular well used in many of the quantum mechanical approaches can even give qualitatively different results. 
N. G. Kelkar, M. Nowakowski
nucl-th