Dineutron structure in $^{8}$He

TL;DR

This paper investigates the structure of $^{8}$He using antisymmetrized molecular dynamics, revealing a potential dineutron condensate state with gas-like dineutron clusters around an alpha core.

Contribution

It introduces a theoretical prediction of a dineutron condensate state in $^{8}$He, characterized by a gas-like dineutron structure similar to alpha condensates in $^{12}$C.

Findings

Identification of a $0^+_2$ state with dineutron gas-like structure.

Evidence of $^{8}$He ground state with mixed coupling features.

Prediction of a dineutron condensate candidate in $^{8}$He.

Abstract

The ground and excited states of $^{8}$He were investigated with a method of antisymmetrized molecular dynamics(AMD). We adopted effective nuclear interactions which systematically reproduce the binding energies of $^4$He, $^6$He and $^8$He. The ground state of $^8$He has both the $j$-$j$ coupling feature($p_{3/2}$ closure) and the $L$-$S$ coupling feature($^4$He$+2n+2n$) with a slight tail of dineutron at the long distance region. The theoretical results give an indication of the $0^+_2$ state with dineutron gas-like structure. The dineutron structure, $^4$He+$2n$+$2n$, of this state is similar to the $3\alpha$-cluster structure of the $^{12}$C($0^+_2$) state which has been interpreted as an $\alpha$ condensate state. Since the $^8$He($0^+_2$) state has a significant overlap with the dineutron condensate wave function where two dineutrons are moving in $S$ wave around the $\alpha$ core with a dilute density, we suggest that this theoretically predicted $0^+_2$ state is a candidate of the dineutron condensate state.