  It is argued that orbital electron-capture decays of neutral $^{142}$Pm atoms
implanted into the lattice of a solid (LBNL experiment) do not fulfil the
constraints of true two-body beta decays, since momentum as well as energy of
the final state are distributed among three objects, namely the electron
neutrino, the recoiling daughter atom and the lattice phonons. To our
understanding, this could be a reason for the non-observation of a periodic
time modulation in the number of electron-capture decays of implanted neutral
$^{142}$Pm atoms.
