Observation of $^{6}$He+$t$ cluster states in $^{9}$Li

TL;DR

This study identifies and characterizes cluster states in the neutron-rich nucleus $^{9}$Li using experimental reactions and theoretical calculations, confirming its clustering structure for the first time.

Contribution

It provides the first experimental evidence and theoretical analysis of $^{6}$He+$t$ cluster states in $^{9}$Li, including spin-parity assignments and structural insights.

Findings

Two resonant states at 9.8 MeV and 12.6 MeV with specific spin-parities

Identification of these states as part of a K$^{}$^{-} band

Extraction of a monopole matrix element supporting clustering

Abstract

$^{6}$He+$t$ cluster states of exited $^{9}$Li have been measured by 32.7 MeV/nucleon $^{9}$Li beams bombarding on $^{208}$Pb target. Two resonant states are clearly observed with the excitation energies at 9.8 MeV and 12.6 MeV and spin-parity of 3/2$^{-}$ and 7/2$^{-}$ respectively. These two states are considered to be members of K$^{\pi}$=1/2$^{-}$ band. The spin-parity of them are identified by the method of angular correlation analysis and verified by the continuum discretized coupled channels (CDCC) calculation, which agrees with the prediction of the generator coordinate method (GCM). A monopole matrix element about 4 fm$^{2}$ for the 3/2$^{-}$ state is extracted from the distorted wave Born approximation (DWBA) calculation. These results strongly support the feature of clustering structure of two neutron-rich clusters in the neutron-rich nucleus $^{9}$Li for the first time.