Measurements of an ortho–para effect in muon-catalyzed fusion in solid deuterium

In order to investigate the dependence of the rate of muon-catalyzed fusion (μCF) on the ortho–para state (in this case, the nuclear spin state) of deuterium molecules, the fusion protons produced in the μCF in solid deuterium with a controlled ortho-para ratio were observed. The measurements were carried out at a temperature of 3.5 K and ratios of ortho deuterium of 66.7% and 99.9%. The ortho–para effect observed in this work was small (the relative difference of fusion proton yield in the converted (ortho 99.9%) case to that in the normal case is −0.100(117)), suggesting evidence against a proposed solid-state effect that is strongly dependent on the ortho–para ratio (also, the rotational state) of deuterium molecules.