A Search forSi32in Natural Silicon

Two samples of quartz that had been exposed to an intense neutron flux have been examined radio-chemically for the presence of 25-day ${\mathrm{P}}^{33}$. Only ${\mathrm{P}}^{32}$, formed presumably from impurities, has been found. Using the limits of detectability and analysis conditions and assuming 0.05 barn for the neutron capture cross section of ${\mathrm{Si}}^{32}$, an upper limit of 4×${10}^{-6\mathrm{}}$ percent results for the abundance of ${\mathrm{Si}}^{32}$ in natural silicon.