Sizes of the neutronв–proton halo in nucleon-stable states of the $^6$Li nucleus

The matter, neutron, and proton radii of nucleon-stable 1$^+$ and 0$^+$ states of the $^6$Li nucleus are studied theoretically within the no-core shell model. The results have been comparatively analyzed with the radii of the 0$^+$ state of the 6He nucleus. To increase the accuracy of calculations, we have developed an extrapolation procedure. A new definition of the quantitative measure has been proposed and justified to describe the properties of a halo formed by loosely bound neutrons and protons in the $A$-nucleon problem. The sizes of the halo in the indicated states of $^6$Li have been calculated for the first time. It has been demonstrated that the sizes of their halos are close to those of the two-neutron halo in $^6$He. Thus, additional reliable evidence of the existence of the neutron–proton halo in the discussed states of $^6$Li has been obtained.