Heidelberg 2015 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 6: Structure and Dynamics of Nuclei 1
HK 6.3: Vortrag
Montag, 23. März 2015, 15:15–15:30, T/HS2
The nuclear isomer transition in Thorium-229: Search for the VUV photon — •Simon Stellmer1, Matthias Schreitl1, Koji Yoshimura2, and Thorsten Schumm1 — 1Atominstitut /TU Wien and VCQ, Vienna, Austria — 2Okayama University, Japan
The isotope 229Th is believed to possess a low-lying nuclear excitation, at an energy of about 7.8(5) eV [1], corresponding to a wavelength of 160(10) nm. Convincing direct evidence of the existence of this state, for instance by observation of its excitation or decay, is still pending.
Optical excitation of the isomer state is an exceptional challenge, as the required wavelength is not known, the transition is believed to be extremely narrow, and the choice of suitable lasers is limited. Instead, we use synchrotron radiation at 29 keV to populate the second excited state, which then decays into the desired isomer state. This state proceeds further into the ground state under emission of the much sought-after VUV photon. This photon is detected in a spectrometer.
The measurements are performed at the SPring-8 facility in Japan; we will report on the latest status of the experiment.
[1] Beck et al., Phys. Rev. Lett. 98, 142501 (2007).