First observation of radiative photons associated with the μ− transfer process from (tμ−) to 3He through an intermediate (t3Heμ−) mesomolecule

For the first time, we have observed the 6.76 keV radiative transition photons associated with the μ− transfer process from (tμ−) atoms to 3He nuclei through intermediate (t 3He μ−) mesomolecule formation in a solid T2 target. The radiative decay branching ratio of the (t 3He μ−) mesomolecule and the muon transfer rate were determined and compared with theoretical values. We also studied an accumulation process of 3He atoms in a solid T2 target by observing the neutron decay rates originating from t–t muon-catalyzed fusions. Their time dependence indicates a sudden 3He bubble formation in the solid T2 at an atomic concentration of 130 ppm.