Thorium-229's excited state at 8.355733554021(8) eV

[mfb]

TL;DR

Frequency comb measurements of thorium's unusually low excited state have measured its energy much more precisely.

Missed this on arXiv, now it's published: Frequency ratio of the ^229mTh nuclear isomeric transition and the ⁸⁷Sr atomic clock
They measure the frequency of the transition radiation with an uncertainty of just 2 kHz or 1 part in a trillion. That's not beating the best atomic clocks yet, but it shows that you can measure this transition with the tools used for atomic clocks - and then exploit the better stability you get from using nuclei instead of atoms.

 

[ohwilleke]

TL;DR Summary: Frequency comb measurements of thorium's unusually low excited state have measured its energy much more precisely.

Missed this on arXiv, now it's published: Frequency ratio of the ^229mTh nuclear isomeric transition and the ⁸⁷Sr atomic clock
They measure the frequency of the transition radiation with an uncertainty of just 2 keV or 1 part in a trillion. That's not beating the best atomic clocks yet, but it shows that you can measure this transition with the tools used for atomic clocks - and then exploit the better stability you get from using nuclei instead of atoms.

Out of respect for the folks who did the work, the authors of the new paper (in the journal Nature) are:

• Chuankun Zhang,
• Tian Ooi,
• Jacob S. Higgins,
• Jack F. Doyle,
• Lars von der Wense,
• Kjeld Beeks,
• Adrian Leitner,
• Georgy A. Kazakov,
• Peng Li,
• Peter G. Thirolf,
• Thorsten Schumm &
• Jun Ye