  Josephson-like junctions, transiently established in heavy ion collisions
between superfluid nuclei, few MeV below the Coulomb barrier, allow for the
back and forth transfer of a nuclear Cooper pair of effectively charged
nucleons and thus the emission of $\gamma$-rays. The second order DWBA
$T$-matrix formulation of single Cooper pair alternating current is shown to
contain the gauge phases and gauge rotational frequencies as required by the
Josephson (ac) effect, in keeping with the derivation of the transfer
(tunneling) Hamiltonian in a gauge invariant representation. We describe the
emergence of two strongly convergent parameters (conserved quantities) within
the time the abnormal densities of the two superfluid nuclei overlap: a) the
correlation length (dc); b) the number of emitted $\gamma$-rays per cycle (ac),
and thus the dipole moment of the successively transferred nucleons. Result
which leads to a nuclear parallel with the direct current (dc) and alternating
current (ac) Josephson effects, and which testifies to the validity of BCS
theory of superconductivity down to few Cooper pair condensates, and single
Cooper pair alternating currents. The physics at the basis of a quantitative
description of Cooper pair tunneling between weakly coupled superconductors or
superfluid nuclei at energies below the Coulomb barrier, is that the process is
dominated by the successive transfer of the two partner fermions entangled over
distances of the order of the coherence length, $\approx10^4$\AA ${}$ in the
case of lead, and 13.5 fm in the case of the reaction
$^{116}\text{Sn}+^{60}\text{Ni}\to^{114}\text{Sn(gs)}+^{62}\text{Ni(gs)}$ at
few MeV below the Coulomb barrier.
