Analyzing Ultra-Precise X-ray Spectroscopy Measurements of Helium-like Uranium

An international research team recently made a groundbreaking breakthrough by conducting ultra-precise X-ray spectroscopic measurements of helium-like uranium. This achievement, led by researchers from Friedrich Schiller University Jena and the Helmholtz Institute Jena in Germany, marks the first successful disentanglement and separate testing of one-electron two-loop and two-electron quantum electrodynamic effects for extremely strong Coulomb fields of the heaviest nuclei. The team’s results have been published in the prestigious journal Nature.

The published paper details the team’s basic research into the fundamental question of what holds our world together at its innermost level. Dr. Robert Lötzsch, an experimental physicist at the Institute of Optics and Quantum Electronics at the University of Jena, highlights the uniqueness of this project in that it focuses on measurements conducted on the heaviest stable atoms. Traditionally, precise measurements of electron transitions were made for hydrogen atoms, which have an atomic number of one, up to an impressive 13 decimal places. In contrast, measurements for uranium, with an atomic number of 92, have only been attained to five decimal places.

The experiments were carried out at the GSI/FAIR experimental storage ring in Darmstadt, which is a particle accelerator complex utilized by multiple European countries. The research involved international study groups from Poland, France, Portugal, and Germany, all working under the leadership of Martino Trassinelli and Robert Lötzsch. The Darmstadt complex consists of an ion storage ring with a circumference exceeding 100 meters and an expansive upstream accelerator that extends for over a kilometer.

To conduct the experiment, first, free ions are generated by vaporizing uranium and rapidly accelerating it to approximately 40% of the speed of light. The resulting material then passes through a special film, causing the loss of electrons in the process. The accelerated electrons are subsequently guided into a storage ring, where they race along a circular path. Up to an astounding 50 million times per second, these particles pass by the researchers’ spectrometers, occasionally undergoing an electron transition that can be measured.

The experiment relies on a special Bragg crystal spectrometer constructed in Jena. The crucial component of this spectrometer is a specifically bent crystal made from germanium. According to Lötzsch, this crystal is incredibly thin, resembling a sheet of paper, and is securely held in a special glass mold. This technique, which demands significant expertise, was developed in Jena and has been a focus of research for over three decades.

The recently published results are the product of an experiment conducted in 2021, spanning three weeks over the Easter holiday period. Despite the complexities caused by the ongoing COVID-19 pandemic, Lötzsch believes that the effort expended was well worthwhile. The team’s success in achieving ultra-precise X-ray spectroscopic measurements of helium-like uranium opens new doors to understanding the intricate mechanisms that govern our physical world at its most fundamental level.

The accomplishments of the international research team in conducting ultra-precise X-ray spectroscopic measurements of helium-like uranium are truly remarkable. Their ability to disentangle and separately test quantum electrodynamic effects for extremely strong Coulomb fields represents a major step forward in our understanding of the atomic world. With applications extending beyond fundamental research, these findings have the potential to influence various fields, from materials science to nuclear physics. The journey to unravel the mysteries of our universe may still be ongoing, but each breakthrough brings us closer to a deeper comprehension of what binds our world together.