Evidence for phonon mediated pairing interaction in the halo of the nucleus 11Li

With the help of a unified nuclear-structure–direct-reaction theory we analyze the reaction 1H(11Li,9Li)3H. The two halo neutrons are correlated through the bare and the induced (medium polarization) pairing interaction. By considering all dominant reaction channels leading to the population of the 1/2- (2.69 MeV) first excited state of 9Li, namely, multistep transfer (successive, simultaneous, and nonorthogonality), breakup, and inelastic channels, it is possible to show that the experiment provides direct evidence of phonon mediated pairing.