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Talks and Poster Presentations (without Proceedings-Entry):

G. Kazakov, M. Schreitl, G. Winkler, J.H. Sterba, G. Steinhauser, Thorsten Schumm:
"Atomic clock with nuclear transition: current status in TU Wien";
accepted as talk for: Isomers in Nuclear and Interdisciplinary Research, Peterhof; 2011-07-04 - 2011-07-10.



English abstract:
Quantum frequency standards find a number of applications in science and engineering. Further progress in improving of quantum frequency standards accuracy opens new possibilities for experimental investigations of basic fundamental laws of physics. The question "Are fundamental constants really constant?" is among them. One of the most promising method of study of this problem is connected with the monitoring of the frequency ratio of two quantum standards whose transition frequencies are mainly determined by different fundamental interactions, for example, if one standard is based on electronic transition in the atomic/ionic shell and other one is based on the nuclear transition [1]. 229Th is the only known isotope with isomer excitation energy attainable by laser.
This energy was measured by study of γ-ray resulting from the decay chain of Uranium-233. Two most accepted values are E = 3.5 ± 1.0 eV [2] and E = 7.6 ± 0.5 eV [3]. No direct evidences of ultraviolet photons emitted from the decay of nucleus isomer are still found. This failure can be connected with discrepancy of real isomer energy with the studied range and with significant decreasing of the lifetime of 229Th isomer state due to interaction with conductivity electrons in metals [4] and with electronic shells [5, 6].
At present time our group and group of E. Hudson [7] are plan to find the photons from isomer transition studying the fluorescence of ionic crystal doped by 229Th ions after illumination by ultraviolet radiation. We expect it will be possible due to a large energy gap in a host crystal the processes of internal conversion and bound internal conversion will be suppressed in comparison with ones in atomic and metallic 229Th. Preliminarily measurements demonstrate the good transparency of CaF2 host crystal doped by 232Th isotope in vacuum ultraviolet range.
This study is supported by FWF, project M 1272-N16, and by ERC, project NAC.

References
1. V.V. Flambaum, Phys. Rev. Lett. 97, 092502 (2006).
2. R.G. Helmer et.al., Phys. Rev. C64, 1845-1858 (1994)
3. B.R. Beck et.al., Phys. Rev. Lett. 98, 142501 (2007).
4. E.V. Tkalya et. al., Phys. Rev. C 61, 064308 (2000)
5. F. F. Karpeshin and M. B. Trzhaskovskaya. Physics of Atomic Nuclei 69, 4, 571 (2006)
6. F. F. Karpeshin and M. B. Trzhaskovskaya. Phys. Rev. C 76, 054313 (2007)
7. W.G. Rellergert et.al., PRL 104, 200802 (2010)

Keywords:
nuclear clock, Thorium, isomer transition,


Electronic version of the publication:
http://publik.tuwien.ac.at/files/PubDat_201187.pdf


Created from the Publication Database of the Vienna University of Technology.