Open AccessThe 229-thorium isomer: doorway to the road from the atomic clock to the nuclear clock
Author(s) -
P. G. Thirolf,
Benedict Seiferle,
Lars von der Wense
Publication year - 2019
Publication title -
journal of physics. b, atomic molecular and optical physics/journal of physics. b, atomic, molecular and optical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 121
eISSN - 1361-6455
pISSN - 0953-4075
DOI - 10.1088/1361-6455/ab29b8
Subject(s) - physics , realization (probability) , excited state , nuclear isomer , atomic nucleus , nuclear physics , decay scheme , gamma ray , statistics , mathematics
The elusive ‘thorium isomer’, i.e. the isomeric first excited state of 229 Th, has puzzled the nuclear and fundamental physics communities for more than 40 years. With an exceptionally low excitation energy and a long lifetime it represents the only known candidate so far for an ultra-precise nuclear frequency standard (‘nuclear clock’), potentially able to outperform even today’s best timekeepers based on atomic shell transitions, and promising a variety of intriguing applications. This tutorial reviews the development of our current knowledge on this exotic nuclear state, from the first indirect evidence in the 1970s, to the recent breakthrough results that pave the way towards the realization of a nuclear clock and its applications in practical fields (satellite based navigational systems and chronometric geodesy) as well as fundamental physics beyond the standard model (the search for topological dark matter and temporal variations of fundamental constants).