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High-precision atomic mass measurement of helium-4


Sasidharan,  Sangeetha
Division Prof. Dr. Klaus Blaum, MPI for Nuclear Physics, Max Planck Society;

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Sasidharan, S. (2023). High-precision atomic mass measurement of helium-4. PhD Thesis, Ruprecht-Karls-Universität, Heidelberg.

Cite as: https://hdl.handle.net/21.11116/0000-000E-04CA-A
Penning-trap mass spectrometry enables a precise determination of atomic masses, supporting sensitive tests of fundamental physics. LIONTRAP (Light Ion TRAP) is a specialized mass spectrometer focused on precise mass measurements of light ions. In this experiment, we currently reach a relative resolution of 10 parts-per-trillion (ppt) and beyond for atomic masses. The measurement principle involves comparing the cyclotron frequencies of the ions under investigation and a carbon ion, which are inversely proportional to their masses. In the scope of this thesis, a high-precision mass measurement of 4He2+ was performed. To this end, a source for gaseous species was developed, and an extensive investigation of the systematics affecting the mass measurements, including image charge shift, lineshape systematics, and others, was conducted. The mass determined herein has a relative precision of 12 ppt. Based on this, the atomic mass of the neutral atom is determined from the binding energies and the electron mass without loss of precision. The mass value exhibits a precision that is 1.3 times greater than the current literature value but deviates from it by 6.6 combined standard deviations. This result contributes to fundamental physics by potentially supporting the improvement of the electron mass via a g-factor determination of 4He+. Towards the end of the thesis, new developments are presented, including a test of the two-ion balance technique to improve the precision of the upcoming mass measurement.