Spectroscopy of narrow, high-lying, low-spin states inNe20

Abstract

The excited states of the 20 Ne nucleus from the ground state to Ex = 25 MeV were investigated with the 22 Ne(p,t) 20 Ne reaction at a beam energy of Ep = 60 MeV using the QDD magnetic spectrometer at iThemba LABS. Narrow, low-spin J π = 0 + , 1 − and 2 + states have been observed for the first time at high excitation energies in 20 Ne, namely at Ex = 17. 67, 18.84, 20.59, 21.16, 21.80 and 22.5 MeV. Shell-model and coupled reaction channel calculations were performed to determine the nature of the newly observed states. Candidates for T = 2 states are proposed at 3.86(5), 4.43(5) MeV and 5.07(5) MeV above the lowest 0 + , T = 2 state at Ex = 16.73 MeV. Two of these T = 2 candidates appear to result from core-excitations in the 0p-shell. The state at Ex = 22.5 MeV, which could not be interpreted by the shell-model calculations, is a tentative candidate for the 5-α cluster state.

Equivalence of generator coordinate Brink cluster model and nonlocalized cluster model and supersolidity of $α$ cluster structure in nuclei

“…The above structure change is consistent with NCM calculations [48] and the BEC four α cluster calculations using the SCM [77]. For 20 Ne, the ground state with five α clusters at the vertices of a trigonal bipyramid [78,79,80,81,82] makes a structure change near the α threshold as the excitation energy increases [36] and near the five α threshold energy well-developed gas-like α cluster BEC superfluid states [67] are expected to appear as observed in recent experiments [83,84] before the five α linear chain structure at higher energies. Fig.…”

Candidates for the 5$α$ condensed state in ${}^{20}$Ne

“…Only a tentative candidate for the 5α condensed state was experimentally proposed. The several 0 + states observed in the 22 Ne(p, t) 20 Ne reaction were examined with the shell-model calculation [14]. It was found that one of the 0 + states at E x = 22.5 MeV was not described by the shell model, and its excitation energy is close to E x = 21.14 MeV where the 5α condensed state is predicted in Ref.…”

The 5α condensate state in 20Ne

“…This provides an important clue to the 5 α condensate state of 20 Ne. Meanwhile, Swartz et al 36 performed reaction experiments 22 Ne( p , t ) 20 Ne, and the excited states up to E x = 25 MeV of 20 Ne were studied at the iThemba LABS. They found that the state at E x = 22.5 MeV cannot be interpreted by the shell-model calculations and could be the 5 α cluster state.…”