Muonic Molecules in Liquid Hydrogen

We have studied the yield and time distribution of 5.5-MeV gamma rays from the fusion reaction $p+d\to {\mathrm{He}}^3+\gamma$. The reaction was catalyzed by muons from the Nevis synchrocyclotron which were stopped in a target containing high-purity liquid hydrogen. A digitron of 30-nsec resolving time was used to study the yield of gamma rays as a function of the time that elapsed between the stopping of a muon and the emission of a gamma ray and as a function of the deuterium concentration, which was varied from 1 ppm to 25%. Analysis of the experimental distributions gives rates (in ${\sec }^{-1\mathrm{}}$) for the following muonic molecular processes: $p\mu +p\to p\mu p, {\lambda }_{\mathrm{pp}}=(1.89\mathrm{}\pm 0.20)\times {10}^6,$ $p\mu +d\to d\mu +p, {\lambda }_e=(1.43\mathrm{}\pm 0.13)\times {10}^{10},$ $d\mu +p\to p\mu d, {\lambda }_{\mathrm{pd}}=(5.80\mathrm{}\pm 0.30)\times {10}^6,$ $p\mu d\to {\mathrm{He}}^3+\gamma , {\lambda }_f=(0.305\mathrm{}\pm 0.010)\times {10}^6.$ The yield of fusion gamma rays was observed to increase with increasing deuterium concentration until it reached a saturation value of (14.0±2.4)% at 1% concentration. At 25% deuterium concentration the yield was observed to increase by a factor of 1.17±0.01 above the saturation yield. This effect is in agreement with a prediction of Wolfenstein and Gershtein. When neon was in solution in the hydrogen at a concentration of 1%, all of the muons transferred to the neon and the disappearance rate of muons bound to neon was measured to be (0.658±0.010)×${10}^6$ ${\sec }^{-1\mathrm{}}$.