Abstract The E0 transition depopulating the first-excited 0 + state in 24Mg has been observed for the first time, and the E0 transition strength determined by electron-positron pair and γ-ray spectroscopy measurements performed using the Super-e pair spectrometer. The E0 transition strength is ρ 2 × 10 3 = 380 ( 70 ) . A two-state mixing model implies a deformation of the first-excited 0 + state of β 2 ≈ 1 and a change in the mean-square charge radius of Δ 〈 r 2 〉 ≈ 1.9 fm 2 , which suggests a significant shape change between the ground state and first-excited 0 + state in 24Mg. The observed E0 strength gives direct evidence of shape coexistence and superdeformation in 24Mg, bringing this nucleus into line with similar behaviour in nearby N = Z nuclei. This result agrees with recent theoretical work on the cluster nature of 24Mg and has potential ramifications for nuclear reactions of astrophysical importance.

中文翻译：

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24Mg 中形状共存和超变形的证据

摘要 首次观察到 E0 跃迁减少了 24Mg 中第一次激发的 0 + 态，并且使用 Super-e 对光谱仪进行了电子 - 正电子对和 γ 射线光谱测量确定了 E0 跃迁强度。E0 过渡强度为 ρ 2 × 10 3 = 380 (70)。双态混合模型意味着 β 2 ≈ 1 的第一激发态 0 + 状态的变形和 Δ 〈 r 2 〉 ≈ 1.9 fm 2 的均方电荷半径的变化，这表明在24Mg 中的基态和首次激发的 0 + 态。观察到的 E0 强度提供了 24Mg 中形状共存和超变形的直接证据，使该核与附近 N = Z 核中的类似行为一致。