A search was made for weak 7.6-Mev electric monopole pairs from the reaction ${\mathrm{Be}}^9(\alpha , n){\mathrm{C}}^{12*}$ using a thin target, 5.7-Mev alpha particles, and a scintillation pair spectrometer. No 7.6-Mev pairs were seen with an intensity as great as 1.6×${10}^{-5\mathrm{}}$ that of 4.43-Mev gamma rays. This result gives a limit of $\frac{{\Gamma }_{\pm e}}{{\Gamma }_{\mathrm{total}}}<1.3\mathrm{}\times {10}^{-4\mathrm{}}$ for the ratio of the partial width for pair emission to the total width of the 7.6-Mev state. If an estimated alpha-particle width of 0.5 ev is taken for the total width of the 7.6-Mev state, then an upper limit of ${\Gamma }_{\pm e}<7\mathrm{}\times {10}^{-5\mathrm{}}$ ev is obtained for the partial width for pair emission of the 7.6-Mev state.

• Received 15 July 1958

DOI:https://doi.org/10.1103/PhysRev.112.931