Neutron Activation Cross Section of Technetium-98

The cross section for the reaction ${\mathrm{Tc}}^{98}(n, \gamma ){\mathrm{Tc}}^{99m}$ was determined by thermal neutron irradiation of a cyclotron-produced sample containing ${\mathrm{Tc}}^{95}$, ${\mathrm{Tc}}^{97m}$, ${\mathrm{Tc}}^{97g}$, ${\mathrm{Tc}}^{98}$, and ${\mathrm{Tc}}^{99}$. The degree of selectivity and background reduction required to permit an accurate measurement of the ${\mathrm{Tc}}^{98}$ content, 2.68±0.54 disintegrations per minute, was attained by means of $\beta -(740-\mathrm{K}\mathrm{e}\mathrm{v} \gamma )$ coincidence counting. At a thermal flux of 2.1±${10}^{12}$ neutrons ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$, a saturation activity of 375±85 dis/min ${\mathrm{Tc}}^{99m}$ per dis/min of ${\mathrm{Tc}}^{98}$ was obtained. Using the latest value of the half-life of ${\mathrm{Tc}}^{98}$, (1.5±0.7)×${10}^6$ years, one finds a cross section of 2.6±1.3 barns. Relative cross sections are also given for the production of several technetium isotopes by bombardment of molybdenum with 10.2-Mev deuterons.