Search for the High Spin Members of the Alpha:2n:Alpha Band in 10Be

Abstract

There is strong evidence that some states in 10Be exhibit a molecular-like α:2n:α configuration. Based on theoretical studies, it appears that the 6.179 MeV 0⁺ state in ¹⁰Be has a pronounced α:2n:α configuration with an α-α inter-distance of 3.55 fm. This is 1.8 times more than the corresponding value for the ¹⁰Be ground state. The 2⁺ state at 7.542 MeV in ¹⁰Be is believed to be the next member of this rotational band. The state at 10.2 MeV was identified as a 4⁺ member in recent experiments. The algebraic model predicts that the next member of this band is the 6⁺ state that should be found around 13 MeV.

An experiment was performed to search for the 6⁺ state in ¹⁰Be at around 13 MeV excitation energy in the excitation function for ⁶He+α scattering, which populated states in the excitation energy range from 4.5 MeV to 8 MeV in ¹⁰Be using a ⁶He rare-isotope beam and a thick helium gas target. No new excited states in ¹⁰Be have been observed. However, stringent limitation on the possible degree of α-clustering of the hypothetical yrast 6⁺ state has been obtained using Monte Carlo methods. We concluded that the high-spin members of the α:2n:α molecular-like rotational band configuration, that is considered to have a 0⁺ bandhead at 6.18 MeV, either do not exist or have small overlap with the ⁶He(g.s.)+α channel.