Muonic X-ray spectroscopy

Negative muons (μ^-) are injected to solid deuterium layer with ion implantations of nuclei (A), and form muonic hydrogen atoms (dμ^-). The dμ- atoms diffuse to collide the implanted nuclei to form muonic (μ^-A) atoms by muon transfer. At the formation process, characteristic muonic X-rays are emitted. The muon mass is 207 times larger than electron mass, and the muonic atom radius is by 207 smaller than ordinary atomic radius. Therefore, muon orbit is located very close to nuclear surface, and muonic X-ray energies are influenced by the charge density distribution (nuclear shape) of the implanted nuclei. By measuring muonic X-ray energies and the isotope energy shifts, precise information on nuclear charge distribution is obtained.

Recently, observations of muonic X-rays from isotope-separated ¹⁴⁸Sm (spherical) and ¹⁵²Sm (deformed) have been completed to study nuclear charge distributions by comparing the results with theoretical calculations.

The apparatus was disassembled, and transported to J-PARC Muon Facility to restart the experiment.