<i>Ab initio</i> coupled-cluster calculations of ground and dipole excited states in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts /><mml:none /><mml:mn>8</mml:mn></mml:mmultiscripts></mml:math>

We perform coupled-cluster calculations of ground- and dipole excited-state properties the 8He halo nucleus with nucleon-nucleon three-nucleon interactions from chiral effective field theory, both without explicit delta degrees freedom. By increasing precision in our via inclusion leading order three-particle three-hole excitations cluster operator, we obtain a ground-state energy charge radius that are consistent experiment, albeit slight under-binding. also investigate excited states induced by electric operator present discussion on Thomas-Reiche-Kuhn sum rules. Finally, compute polarizability, providing theoretical benchmark for future experimental determinations will study this exotic nucleus.