In the alpha decay of U-233, how many percent of the atoms go into the Th-229 isomer?

The alpha decay of U-233 is a well-established approach to obtain Th-229 atoms or ions in the isomeric state. In fact, it is the only method to date that has been shown to be capable of populating the isomer. Still, the probability of feeding the isomer has not been measured. A value of 2% is often found in literature, yet retracing how this number was obtained is difficult.

We used the available U-233 decay data from the NuDat database and, based on this data, calculated a probability of at least 1.98% for the isomer population. The NuDat data was generated by estimating or assuming a set of branching ratios for gamma and internal conversion transitions. The NuDat database can therefore be used as a reference for the 2%-value, but this value is based on estimated (not measured) branching ratios.

A short essay on the topic can be found here, questions and comments to the author are more than welcome!

Happy New Year 2017

We hope you all had a joyful holiday season. With 2017 just around the corner, nuClock wishes peace, luck, and success in 2017 to all of you: the partners, associates, fans & followers, and all your family and friends. Happy New Year!

“Physics World” 2016 Breakthrough of the Year

Towards the end of each year, the editors of the “Physics World” elect ten experiments or publications that they consider to be the most important scientific breakthroughs of the past year. Although an entirely subjective choice, this “Top-10” list has gained quite some visibility over the past years. To our great delight, the direct detection of the the Th-229 isomer by the LMU Munich group was ranked third among the ten breakthroughs of 2016! Congratulations to Lars, Bene, and Peter from Munich, and to their collaborators at GSI, Mainz, and elsewhere!

This year’s number-one went to be the discovery of gravitational waves by the LIGO collaboration. The magazine “Physics World” and the corresponding webpage are published by the British Institute of Physics (IOP), the full story can be found here.

Laser spectroscopy of Th-229 recoil ions

In a joint experiment of the LMU group and the PTB group a first run of laser spectroscopy experiments has been done on trapped Th-229 from the Munich recoil ion catcher, with laser systems and optical detection methods developed at PTB. The measurements should provide crucial information on the nuclear properties of the isomeric state from the hyperfine structure of electronic transitions. The first experimental campaign in October/November this year has proven the joint working of the systems and has yielded first spectra. A detailed data analysis requires more reference spectra from ground state Th-229 to be measured at PTB.


PTB researcher Johannes Thielking working on the experiment at LMU Munich.

Laser spectroscopy of Nobelium

Nobelium is one of these heavy and short-lived elements at the bottom of the periodic table. It has a  nuclear charge Z = 102 and even its most stable isotope has a half-life of less than a minute. Elements with Z > 100 are called transfermium elements, and so far, no laser spectroscopy has ever been performed on these elements.

Last week, Mustapha Laatiaoui and his team reported on the first laser spectroscopy of two nobelium isotopes. They used the GSI facility to produce No-252 and No-254, deposited a few of these atoms on a filament, then quickly heated the filament to release the atoms into the gas phase, and performed resonance ionization via an intermediate step; the produced ions were then detected. This very efficient spectroscopy and detection scheme allowed the researches to perform the measurements with the veeery small production rate of these atoms.

Mustapha and his team at GSI are associate partners of the nuClock consortium. Congratulations to this beautiful result!

link to the Nature publication

link to the GSI press release

Deborah Jin 1968 – 2016

We are deeply saddened to learn that Debbie left us much too soon. She was a great physicist and a kind person. Our thoughts are with her family, colleagues, and friends.

nuClock at Ars Electronica 2016

The 2016 Ars Electronica Festival took place last week in Linz: a perfect venue for the first public appearance of nuClock’s art project! Kerstin Ergenzinger presented her past & future work, and Thorsten Schumm took part in a podium discussion on future plans of strengthening the arts/science collaboration in Europe.

Simon Stellmer and Kerstin Ergenzinger on the “Future Innovators Summit” stage, presenting the concept of the nuClock artwork currently under development. (credits: FEAT)

nuClock coordinator Thorsten Schumm (at the microphone) at a podium discussion among researchers, artists, and policy makers. (credits: FEAT)

Leibinger Innovation Prize for TOPTICA Guide Star Laser

On September 9th 2016, TOPTICA’s guide star laser SodiumStar 20/2 was rewarded with the third place of the highly prestigious Laser Research Innovation Award presented by the Berthold Leibinger Stiftung. The “Guide Star Alliance”, consisting of TOPTICA Photonics AG (Germany), MPB Communications Inc. (Canada) and the European Southern Observatory (ESO), developed a novel high power laser system over a period of more than seven years serving as Guide Star for the Very Large Telescope (VLT) and other Large and Extremely Large Telescopes (ELT). This technology is a very long sought for key component for the construction of modern, earth-based telescopes and it has created already a large impact in the performance, reliability and maintenance of such high-tech devices.

Read more about the award ceremony in the official press release of the Berthold Leibinger Stiftung here.

Read more about the Guide Star Laser technology in this Laser Focus World article here.

On 26 April 2016 an event at ESO’s Paranal Observatory in Chile marked the brilliant first light for the four powerful lasers that form a crucial part of the adaptive optics systems on ESO’s Very Large Telescope. Attendees were treated to a spectacular display of cutting-edge laser technology against the majestic skies of Paranal. These are the most powerful laser guide stars ever used for astronomy and mark the first use of multiple laser guide stars at ESO. This spectacular image shows the four beams emerging from the new laser system on Unit Telescope 4 of the VLT.

Four units of TOPTICA’s laser guide star system “SodiumStar 20/2” project powerful orange beams into the air in Chile’s Atacama desert at the VLT. (Credit: ESO/F. Kamphues)


The third place of the 2016 Leibinger award for Laser Research Innovation was given to TOPTICA’s Guide Star Laser project. (Credit: Berthold Leibinger Foundation)


Congratulations to TOPTICA!

nuClock FEAT prepares for first exhibition

A few months ago, nuClock joined the FEAT initiative to explore the interplay between arts and sciences. The cooperation with artist Kerstin Ergenzinger of Berlin will come to life at the upcoming Ars Electronica exhibition in Linz, Austria. Ars Electronica is the world’s largest and most influential exhibition of digital art. Held annually since 1979, it is set up as a 4-day festival with a focus on the interface between arts, electronics, and society. The motto of this year’s meeting is “RADICAL ATOMS and the alchemists of our time”: what a picture-perfect setting for our nuClock work! The event will last from September 8 through 10, and is expected to attract 600 exhibitors and 100.000 visitors.

nuClock will be featured on the opening day, Thursday Sept. 8. At first, Kerstin Ergenzinger and Simon Stellmer will have an interview with Annick Bureaud, which will later morph into a video blog. Later, the two will present the concept of nuClock’s first piece of art: an installation that builds on earlier “navigating noise” artwork. In addition, Thorsten Schumm will join a podium discussion on arts and sciences.

To prepare for the exhibition, Simon Stellmer spent a two-day visit at Kerstin Ergenzinger’s studio in Berlin last week. In turn, Mrs. Ergenzinger visited the MLS facility in Berlin-Adlershof, where a joined TU WIEN / PTB experiment is currently prepared to search for the Th-229 isomer transition. This measurement – detecting a faint signal on top of large background noise – is the inspiration for the joint artwork.

ICAP 2016 in Seoul

The 25th International Conference on Atomic Physics (ICAP) is currently taking place in Seoul. This series of conferences is probably the largest, oldest, and most prestigeous series of conferences in the field of atomic & quantum physics. Held only every other year, this year’s conference attracted some 500+ participants to the main conference, but also to the various satellite meetings arranged around it. The nuClock consortium is represented by four groups: PTB (Ekkehard Peik), MPQ (Thomas Udem), TU Wien (Simon Stellmer), and Toptica Photonics (Stephan Falke). They are joined by a number of other thorium enthusiasts: Dave DeMille (Yale), Oscar Herrera-Sancho (ex PTB, now Innsbruck & Costa Rica), Atsushi Yamaguchi (ex PTB, now RIKEN), as well as Noboru Sasao, Takahiko Masuda, and Hideaki Hara (all Okayama University). You asked about the venue? It’s the famous COEX center, right in the middle of the world-famous Gangnam district. More information can be found at the conference webpage.