We propose to search for neutron halo isomers populated via $\gamma$-capture in stable nuclei with mass numbers of about A=140\textendash{}180 or A=40\textendash{}60, where the 4s 1/2 or 3s 1/2 neutron shell model state reaches zero binding energy. These halo nuclei can be produced for the first time with new $\gamma$-beams of high intensity and small band width ($\leq$0.1%) achievable via Compton back-scattering off brilliant electron beams, thus offering a promising perspective to selectively populate these isomers with small separation energies of 1 eV to a few keV. Similar to single-neutron halo states for very light, extremely neutron-rich, radioactive nuclei (Hansen et al. in Annu. Rev. Nucl. Part. Sci. 45:591\textendash{}634, 1995; Tanihata in J. Phys. G., Nucl. Part. Phys. 22:158\textendash{}198, 1996; Aumann et al. in Phys. Rev. Lett. 84:35, 2000), the low neutron separation energy and short-range nuclear force allow the neutron to tunnel far out into free space much beyond the nuclear core radius. This results in prolonged half-lives of the isomers for the $\gamma$-decay back to the ground state in the 100 ps-$\mu$s range. Similar to the treatment of photodisintegration of the deuteron, the neutron release from the neutron halo isomer via a second, low-energy, intense photon beam has a known much larger cross section with a typical energy threshold behavior. In the second step, the neutrons can be released as a low-energy, pulsed, polarized neutron beam of high intensity and high brilliance, possibly being much superior to presently existing beams from reactors or spallation neutron sources.     «

We propose to search for neutron halo isomers populated via $\gamma$-capture in stable nuclei with mass numbers of about A=140\textendash{}180 or A=40\textendash{}60, where the 4s 1/2 or 3s 1/2 neutron shell model state reaches zero binding energy. These halo nuclei can be produced for the first time with new $\gamma$-beams of high intensity and small band width ($\leq$0.1%) achievable via Compton back-scattering off brilliant electron beams, thus offering a promising perspective to selectively...     »