The hyperfine splitting of the 5g→4f transitions in muonic Re185,187 has been measured using high resolution high purity germanium detectors and compared to state-of-the-art atomic theoretical predictions. The spectroscopic quadrupole moment has been extracted using modern fitting procedures and compared to the values available in literature obtained from muonic x rays of natural rhenium. The extracted values of the nuclear spectroscopic quadrupole moment are 2.07(5) b and 1.94(5) b, respectively for Re185 and Re187.
Bibliographical noteFunding Information:
We gratefully thank L. Simons for many valuable discussions. This work was supported by the Paul Scherrer Institut through the Career Return Programme, by the Swiss National Science Foundation through the Marie Heim-Vögtlin Grant no. 164515 and project Grant no. 200021_165569, by the Cluster of Excellence “Precision Physics, Fundamental Interactions, and Structure of Matter” (PRISMA EXC 1098 and EXC 2118/1) funded by the German Research Foundation (DFG) within the German Excellence Strategy (Project ID 39083149). F.W. has been supported by the German Research Foundation (DFG) under Project No. WA 4157/1. Most of the theory results in this article are part of the PhD thesis work of N.M., which was published at the Heidelberg University, Germany. The experiment was performed at the beam line of PSI. We would like to thank the accelerator and support groups for the excellent conditions. Technical support by F. Barchetti, F. Burri, M. Meier, and A. Stoykov from PSI and B. Zehr from the IPP workshop at ETH Zürich is gratefully acknowledged. This work is part of a larger effort at the Paul Scherrer Institut towards the measurement of the nuclear charge radii of radioactive elements.