Bremsstrahlung in α decay of ²¹⁰ po: Do α particles emit photons in tunneling?

Emission probability of bremsstrahlung in the α decay of ²¹⁰Po was measured in α- γ coincidence measurements with Si and Ge detectors. It was found that the bremsstrahlung yields are much smaller than those predicted by a Coulomb acceleration model, in which γ rays are emitted during acceleration outside the barrier. This suggests that the radiation amplitude in the barrier cannot be neglected, and the discussion based on a quasiclassical approach is given.