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A: Fachverband Atomphysik
A 7: Precision spectroscopy of atoms and ions I
A 7.7: Vortrag
Montag, 9. März 2020, 15:45–16:00, f107
In Search for the Unobserved Low Lying Atomic Energy Levels of Actinium — •Ke Zhang1,2, Dominik Studer2, Vadim Gadelshin2, Felix Weber2, Nina Kneip2, Tom Kieck1,2, Sebastian Raeder1,2, Dmitry Budker1,2, and Klaus Wendt2 — 1Helmholtz Institute Mainz, 55099 Mainz, Germany — 2Johannes Gutenberg-University Mainz, 55099 Mainz, Germany
Actinium (Z = 89) is the name giver and the first member of the series of actinides. Based upon its ground state configuration 7s26d 2D3/2, the element exhibits a highly complex atomic structure. Recently 86 energy levels in the energy range between 0 cm−1 and 36 218 cm−1 have been predicted by theory, from which so far only 28 level energies have been confirmed experimentally. In particular the lowest lying missing odd levels 7s2 7p 2P1/2o and 7s2 7p 2P3/2o, predicted at 7565 cm−1 and 12 345 cm−1, which are accessible by direct laser excitation from the atomic ground state, are of high relevance to test the theoretical description of the Ac spectrum. We utilize two-step resonance ionization spectroscopy with high repetition rate pulsed Titanium: sapphire lasers operating on about 1010 atoms in a hot cavity ion source at the Mainz university atomic beam apparatus MABU. The study of these optical transitions involves direct non-resonant ionization into the continuum beyond 43 394.45 cm−1. For the first infrared transition to excite the 2P1/2o level, predicted at 1321.8 nm, difference frequency generation is needed, while the ionization step employs 279 nm light generated by frequency tripling.