Gamma-Rays Associated with Selected Neutron-Induced Radioactivities

By means of photographic magnetic spectrometers located close to the heavy water moderated reactor, the following radioactive nuclei have been examined: Se⁷⁷ᵐ (17.5 sec), Se⁷⁹ᵐ (3.5 min), Se⁸¹ᵐ (58 min), Se⁸¹ (17 min), Se⁸³ (69 sec), Se⁸³ (26 min), Nd¹⁴⁷ (11.9 days), Nd¹⁴⁹ (1.8 hr), Nd¹⁵¹ (12 min), Pm¹⁴⁹ (50 hr), Pm¹⁵¹ (27.5 hr), Sm¹⁴⁵ (410 days), Sm¹⁵¹ (>20 yr), Sm¹⁵³ (46.5 hr), Sm¹⁵⁵ (23.5 min), Eu¹⁵⁵ (1.7 yr), Mo¹⁰¹ (14 min), Tc¹⁰¹ (15 min), and Th²³³ (23.6 min). The 27.5-hour activity assigned to Pm¹⁵¹ was discovered in this work. A new vacuum gate for the camera of the spectrometer permits the study of activities with half-lives as short as ten seconds. Energy level schemes for the product nuclei are proposed on the basis of a spectrographic analysis of the gamma-rays and also of coincidence and absorption measurements. Changes in spin and parity between many of the energy levels are determined from measurements of the K/L ratios of the corresponding gamma-rays.