Speaker
Description
More than 60 years ago, Macfarlane and Siivola proposed that the proximity of the doubly magic nucleus ¹⁰⁰Sn would strongly enhance the α decay of N≈Z tellurium isotopes, with the ¹⁰⁰Sn+α system behaving as a molecule-like configuration [1]. This conjecture frames a central question in the physics of α radioactivity, how and where the α particle preforms before emission, for which the decay of a nucleus into a doubly magic daughter is the most stringent testing ground [2]. The search for ¹⁰⁴Te α decay was pursued over the last two decades through studies of the heavier tellurium and xenon isotopes and their decay chains [3–6], culminating in the 2018 identification of the ¹⁰⁸Xe→¹⁰⁴Te→¹⁰⁰Sn chain, which placed only an upper limit of T1/2 (¹⁰⁴Te) < 18 ns [7].
Reported here is a definitive measurement of the ¹⁰⁴Te lifetime. The degree of decay enhancement observed in this work exceeds existing model predictions [8–11], raising the question of whether current α-emission models are complete. ¹⁰⁴Te occupies a singular position on the chart of nuclides: it has equal numbers of protons and neutrons and can α decay directly to doubly magic ¹⁰⁰Sn. I will discuss the experimental efforts that led to this discovery, place it in a theoretical context, and examine the models that attempt to explain the enhancement of ¹⁰⁴Te α-particle emission.
This research was partly sponsored by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-FG02-96ER40983 (UTK). This work was also sponsored by the Stewardship Science Academic Alliances program through DOE Awards No. DE-NA0004068.
References
[1] R. D. Macfarlane and A. Siivola, "New region of alpha radioactivity," Phys. Rev. Lett. 14, 114 (1965). 10.1103/PhysRevLett.14.114
[2] H. J. Mang, "Calculation of α-transition probabilities," Phys. Rev. 119, 1069 (1960). 10.1103/PhysRev.119.1069
[3] D. Schardt et al., "Alpha decay studies of tellurium, iodine, xenon, and cesium isotopes," Nucl. Phys. A 326, 65 (1979).
[4] R. D. Page et al., "Alpha radioactivity above ¹⁰⁰Sn including the decay of ¹⁰⁸I," Phys. Rev. C 49, 3312 (1994). 10.1103/PhysRevC.49.3312
[5] D. Seweryniak et al., "Population of the 168-keV (g₇/₂) excited state in ¹⁰³Sn in the α decay of ¹⁰⁷Te," Phys. Rev. C 66, 051307(R) (2002). 10.1103/PhysRevC.66.051307
[6] S. N. Liddick et al., "Discovery of ¹⁰⁹Xe and ¹⁰⁵Te: superallowed α decay near doubly magic ¹⁰⁰Sn," Phys. Rev. Lett. 97, 082501 (2006). 10.1103/PhysRevLett.97.082501
[7] K. Auranen et al., "Superallowed α decay to doubly magic ¹⁰⁰Sn," Phys. Rev. Lett. 121, 182501 (2018). 10.1103/PhysRevLett.121.182501
[8] P. Mohr, "α-nucleus potentials, α-decay half-lives, and shell closures for superheavy nuclei" / ¹⁰⁴Te prediction, Eur. Phys. J. A 31, 23 (2007). 10.1140/epja/i2006-10168-7
[9] S. Yang, C. Xu, G. Röpke et al., "α decay to a doubly magic core in the quartetting wave function approach," Phys. Rev. C 101, 024316 (2020). 10.1103/PhysRevC.101.024316
[10] R. M. Clark et al., "Enhancement of α-particle formation near ¹⁰⁰Sn," Phys. Rev. C 101, 034313 (2020). 10.1103/PhysRevC.101.034313
[11] F. Mercier et al., "Microscopic description of the self-conjugate ¹⁰⁸Xe and ¹⁰⁴Te α-decay chain," Phys. Rev. C 102, 011301(R) (2020). 10.1103/PhysRevC.102.011301
[12] I. C. Cox, R. Grzywacz et al., "Direct observation of the superallowed α-decay of ¹⁰⁴Te," Nature (2026). 10.1038/s41586-026-10581-w