Heterogeneous exchange reactions of unstable simple systems

The analysis of less than 10⁻⁹ g of the isotope²⁰⁴Pb in lunar samples was carried out by an (n, 2n) activation using high energy (>8. 8 MeV) neutrons. A procedure of using the neutrons produced by bombardment of a specially designed Be sample holder with deuterons in a cyclotron was developed and compared to irradiation carried out in the core of a nuclear reactor, Radiochemical separations and X ray-γ ray coincidence counting techniques are necessary to achieve the required sensitivity. Although the flux of neutrons of sufficient energy from the cyclotron procedure is somewhat lower can be obtained in the best reactor irradiations, the high radioactivity due to other elements produced by the (n, γ) reactions in the reactor is eliminated. Radiochemical procedures for the analysis of Bi, Tl, Zn in the same samples are also described.