Resonances inC14observed in theHe4(10

Abstract

The α( 10 Be, α) 10 Be resonant scattering reaction has been measured at nine 10 Be beam energies from 25 to 48 MeV, scanning out resonances in 14 C from excitation energies of 13 to 24 MeV. Angular distribution measurements were used to assign the spin and parity of 5 − to resonances at E x = 18.82(2) and 19.67(2) MeV and 6 + at E x = 20.80(2) MeV. The data also strongly indicate a 3 − resonance at 17.32(2) MeV. The systematic uncertainty on the excitation energies is 175 keV. An R-matrix analysis has been performed for the excitation energy range 16.5 to 22 MeV. The data are discussed in terms of cluster bands in 14 C.

Three-body decay of linear-chain states in C14

“…The first band, which we call a π -bond linear chain, has two valence neutrons in a π orbit and is built on the 0 + state at 14.6 MeV which is just above the α + 10 Be threshold but below the 2α + 6 He threshold. It was found that the energies and widths of the resonances observed by the α + 10 Be elastic scattering [36,37] qualitatively agree with the theoretical calculations [15,18] including ours. Therefore, they are regarded as the π -bond linear-chain candidates, although the experimental spin-parity assignment was somewhat ambiguous.…”

“…Yamaguchi et al [39] reported the result of the α + 10 Be elastic scattering and updated the information about the candidates of the π -bond linear chain. Although the spin-parity assignments for several states are not consistent with those found in previous experiments [35][36][37]39], they first observed a candidate of the bandhead of the linear chain (J π = 0 + ), which should be compared with theoretical calculations. The other experiment was reported by Tian et al [40] and Li et al [41] who observed the resonances populated by the 9 Be( 9 Be,α + 10 Be)α reaction.…”

“…Figure 3 summarizes the calculated rotational bands with the linear-chain configurations presented in Ref. [22] and experimental data [36,37,39,40]. The π -bond linear-chain band shown by blue squares is built on the 0 + state at 14.6 MeV which lies just above the α + 10 Be(0 of the linear-chain bands are as follows: First, these bands are dominated by the intrinsic states having the linear-chain configurations shown in Fig.…”

“…The first choice is a = 5.2 fm which is common to the value used in the R-matrix analysis of the π -bond linear-chain candidates observed in Ref. [36] and close to that in Ref. [39].…”

“…It was pointed out that the motion of the valence neutron can be qualitatively interpreted in terms of the molecular orbits analogous to the Be isotopes [23][24][25][26][27][28][29], which are called π and σ orbits. Concurrently, rather promising candidates of the linear chain were reported in 14 C and 16 C by several experiments [30][31][32][33][34][35][36][37][38]. In our previous study [22], based on an antisymmetrized molecular dynamics (AMD) calculation, we pointed out that two positive-parity rotational bands in 14 C have the linear-chain configurations.…”