Nuclear Josephson-like γ-emission*

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 effective charged nucleons and thus the

emission of γ-rays. The semiclassical description 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. The fact that such reaction description is equivalent to a second order DWBA

T-matrix formulation extensively used in the study of pairing rotational bands with two-particle transfer reactions, together with

the nuclear structure result that the BCS condensation order parameter  α₀= Σ_ν>0 U_ν V_ν (number of Cooper pairs), sum of the coherence factors U_ν V_ν (two-nucleon transfer spectroscopic amplitudes), is quite stable with respect to model description, is found to be connected with 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 γ-rays per cycle (ac), and thus the dipole moment of the successively transferred nucleons. Result which leads to a consistent 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.