Neutron halo effect on direct neutron capture and photodisintegration

Analytical E1 strength functions of two-neutron halo nuclei: the 6He example

“…2 several experimentally measured strength functions for 6 He and 11 Li are compared in the described way. The spectra are plotted as functions of the parameter x = E/E 0 .…”

“…In the direct breakup mechanism, low-energy dipole excitations occur as a natural consequence of the small binding energy or correspondingly of the large distance between the charge and the center of mass (CM) of a halo nucleus. In this way the E1 strength function of the one-neutron halo nucleus 11 Be can be explained using a simple two-body model with a Yukawa wave function (WF) for the initial state and plane waves in the final state [10,11]. However, for two-neutron halo nuclei, like 6 He, 11 Li, and 14 Be, a three-body picture is more appropriate but also more complicated.…”

“…In this way the E1 strength function of the one-neutron halo nucleus 11 Be can be explained using a simple two-body model with a Yukawa wave function (WF) for the initial state and plane waves in the final state [10,11]. However, for two-neutron halo nuclei, like 6 He, 11 Li, and 14 Be, a three-body picture is more appropriate but also more complicated. Microscopic three-cluster calculations of the E1 strength function were performed for, e.g., 6 He [9,12].…”

“…As a test case the E1 strength function of 6 He is studied and compared with the experimental data of Aumann et al [14]. In a subsequent paper the model will be applied to 11 Li and 14 Be. In Sec.…”

“…However, it is still an open question whether this is a true resonant state, which is being observed through the E1 excitation. For example, intensive studies of the oneneutron halo nucleus 11 Be have shown a very significant enhancement of the E1 strength just above the 10 Be + n threshold where there are no resonances in 11 Be. For 6 He several different three-body approaches [3,[6][7][8][9] agree that there is no low-lying 1 − resonant state in the continuum.…”