Background: The energy distribution of excited states populated by the
nuclear muon capture reaction can facilitate an understanding of the reaction
mechanism; however, experimental data are fairly sparse. Purpose: We developed
a new methodology, called the in-beam activation method, to measure the
production probability of residual nuclei by muon capture. For the first
application of the new method, we have measured muon-induced activation of five
isotopically-enriched palladium targets. Methods: The experiment was conducted
at the RIKEN-RAL muon facility of the Rutherford Appleton Facility in the UK.
The pulsed muon beam impinged on the palladium targets and gamma rays from the
beta and isomeric decays from the reaction residues were measured using
high-purity germanium detectors in both the in-beam and offline setups.
Results: The production branching ratios of the residual nuclei of muon capture
for five palladium isotopes with mass numbers A = 104, 105, 106, 108, and 110
were obtained. The results were compared with a model calculation using the
particle and heavy ion transport system (PHITS) code. The model calculation
well reproduces the experimental data. Conclusion: For the first time, this
study provides experimental data on the distribution of production branching
ratios without any theoretical estimation or assumptions in the interpretation
of the data analysisComment: 20 pages, 11 figure