Neutron halos in the excited states of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi mathvariant="normal">B</mml:mi><mml:mprescripts /><mml:none /><mml:mn>12</mml:mn></mml:mmultiscripts></mml:math>
Physical review. C