Why do entangled proton pairs pass through the coulomb barrier of a heavy
element nucleus with high probability in collisions with energies well
below those required to breach this barrier?

This curiosity has been observed is heavy low energy ion collision studies.


This letter presents evidence that (1) 2p transfer (and

not _-particle transfer) is the dominant transfer process

leading to _Z = 2 events in the reaction 16O+208Pb at

energies well below the fusion barrier, and (2) 2p transfer

is significantly enhanced compared to predictions assum-

ing the sequential transfer of uncorrelated protons, with

absolute probabilities as high as those of 1p transfer at

energies near the fusion barrier.

Measurements of transfer probabilities in various reac-

tions and at energies near the fusion barrier have there-

fore been utilized to investigate the role of pairing corre-

lations between the transferred nucleons. Pairing effects

are believed to lead to a significant enhancement of pair

and multi-pair transfer probabilities [2, 4{7]. Closely re-

lated to the phenomenon of pairing correlations is the

nuclear Josephson effect [8], which is understood as the

tunneling of nucleon pairs (i.e. nuclear Cooper-pairs)

through a time-dependent barrier at energies near but be-

low the fusion barrier. This effect is believed to be similar

to that of a supercurrent between two superconductors

separated by an insulator. An enhancement of the trans-

fer probability at sub-barrier energies is therefore com-

monly related to the tunneling of (multi-)Cooper-pairs

from one superfluid nucleus to the other [2].

NOTE: this experiment was done with both nuclei being doubly-magic with a
closed shell of protons and neutrons…just like nickel.

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