The Induced Radioactivity of Calcium

A study has been made of the radioactivities induced in calcium by bombardment with high energy deuterons, alpha-particles and neutrons. Following irradiation by deuterons, the active samples have been separated chemically into fractions containing scandium, calcium and potassium. Most of the activity was found in the scandium precipitate, the decay curve of which has been analyzed into three components with half-lives of 53±3 minutes, 4.0±0.1 hours, and 52±2 hours. The thick target yields of these active isotopes computed for an infinite duration of bombardment are 5.4×${10}^7$, 3.6×${10}^7$ and 3×${10}^8$ deuterons per active atom. It is suggested that these periods are to be associated with ${\mathrm{Sc}}^{44}$, ${\mathrm{Sc}}^{43}$ and ${\mathrm{Sc}}^{41}$, respectively. The active calcium has been found to be due to ${\mathrm{Ca}}^{45}$, the half-life of which is 2.4±0.2 hours. The thick target yield of this isotope is approximately 9.0×${10}^8$ deuterons per active atom. The 4-hour period has been identified with ${\mathrm{Sc}}^{43}$, as the intense activity observed when calcium was bombarded with 0.2 microampere of 11 Mev alphaparticles decays with a single period of this value. The yield of ${\mathrm{Sc}}^{43}$ in this reaction is one active atom for 2×${10}^5$ alpha-particles. ${\mathrm{Ca}}^{45}$ has also been produced by activating calcium with slow neutrons and by bombarding titanium with fast neutrons. It is shown that the 16-hour period previously reported was probably due to magnesium or sodium impurity and not to the formation of ${\mathrm{K}}^{42}$, as the period of this isotope has been found to be 12.2±0.2 hours.