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Three-body resonances in He-6, Li-6, and Be-6, and the soft dipole mode problem of neutron halo nuclei

Attila Csoto
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Abstract

Using the complex scaling method, the low-lying three-body resonances of $^6$He, $^6$Li, and $^6$Be are investigated in a parameter-free microscopic three-cluster model. In $^6$He a 2$^+$, in $^6$Li a 2$^+$ and a 1$^+$, and in $^6$Be the 0$^+$ ground state and a 2$^+$ excited state is found. The other experimentally known 2$^+$ state of $^6$Li cannot be localized by our present method. We have found no indication for the existence of the predicted 1$^-$ soft dipole state in $^6$He. We argue that the sequential decay mode of $^6$He through the resonant states of its two-body subsystem can lead to peaks in the excitation function. This process can explain the experimental results in the case of $^{11}$Li, too. We propose an experimental analysis, which can decide between the soft dipole mode and the sequential decay mode.

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Attila Csoto. 1994-01-11. Three-body resonances in He-6, Li-6, and Be-6, and the soft dipole mode problem of neutron halo nuclei. https://doi.org/10.1103/physrevc.49.3035

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