The halo of the exotic nucleus 11Li: a single Cooper pair F. Barranco, P.F. Bortignon, R.A. Broglia, G. Colò and E. Vigezzi Eur. Phys. J. A, 11 4 (2001) 385-392 Published online: 15 August 2001 DOI: 10.1007/s100500170050