最速でα崩壊するテルル104の寿命測定に成功 －2重魔法核の近傍で極端に強いαクラスターの形成を発見－

2026-025-28 理化学研究所,東京大学,テネシー大学,オークリッジ国立研究所

¹²⁴Xeから¹⁰⁸Xe、¹⁰⁴Teを経て2重魔法核¹⁰⁰Snに至る過程

＜関連情報＞

• https://www.riken.jp/press/2026/20260528_1/index.html
• https://www.nature.com/articles/s41586-026-10581-w

104Teの超許容α崩壊の直接観測 Direct observation of the superallowed α-decay of 104Te

Ian Cox,Robert Grzywacz,T. T. King,K. P. Rykaczewski,S. Nishimura,R. Yokoyama,N. Fukuda,N. Kitamura,S. Go,C. Mazzocchi,J. M. Allmond,A. Augustyn,N. Braukman,P. Brionnet,A. Esmaylzadeh,J. Fischer,G. Garcia de Lorenzo,S. Hanai,D. Hoskins,N. Imai,K. Kolos,A. Korgul,B. Kreider,S. Michimasa,… M. Yoshimoto
Nature  Published:27 May 2026
DOI:https://doi.org/10.1038/s41586-026-10581-w

Abstract

The radioactivity of the α particle is among the most compelling evidence for the existence of cluster structures in atomic nuclei. During the decay process, a pre-existing α particle tunnels through the potential barrier formed by the residual nucleus^1,2. The degree of preformation of the α particle, a strongly bound system of two protons and two neutrons, is extracted from the data by dividing the α-decay probability by the barrier penetrability for a given particle energy. The preformation probability changes rapidly near nuclear shell closures, which is direct evidence that clustering is connected to nuclear structure³. Enhanced preformation was observed in the lightest α-particle emitters, spherical tellurium and xenon isotopes decaying to magic isotopes of tin. Here we show the most extreme case of α-particle preformation from the measurement of the decay of tellurium-104 (¹⁰⁴Te). With a half-life of 7.2^+2.3-1.5 ns , ¹⁰⁴Te is the fastest ground-state α-emitting nucleus known so far. The deduced preformation demonstrates that the enhancement is greater for ¹⁰⁴Te than for any other nucleus. One nuclear model that can explain our observation postulates that the α particle can exist only in the low-nuclear-matter-density regions on the surface of the nucleus. The uniquely high preformation for ¹⁰⁴Te is attributed to its relation to doubly magic tin-100 (¹⁰⁰Sn), creating conditions conducive to form an α particle.