Production and Characterization of Barium and Radium-226 Targets via Molecular Plating for Muonic Atom Spectroscopy

Muonic atom spectroscopy requires thin, high-quality targets to enable precise measurements of nuclear charge radii. Molecular plating has emerged as a promising technique for preparing such targets, especially when dealing with scarce or radioactive isotopes. In this work, we focus on the production and characterization of barium and Ra-226 targets prepared via molecular plating for use in muonic atom spectroscopy. Barium, being non-radioactive and chemically similar to radium, serves as a suitable surrogate for method development. We successfully prepared thin, uniform barium targets with deposition yields close to 100%, as confirmed by inductively coupled plasma–optical emission spectrometry, autoradiography, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. These targets met the stringent requirements for muonic atom experiments and were utilized in successful spectroscopy measurements. However, when applying the same molecular plating technique to Ra-226, we encountered significant challenges. The radium target exhibited a thick, non-uniform layer with poor adhesion, likely due to the co-deposition of unwanted materials induced by radiolysis of the organic solvent. These findings provide valuable insights for refining target preparation techniques in future experiments involving radioactive isotopes.