Gamma-gamma Coincidence Measurements Research Articles

Radiations ofTe127andTe127m

The radiations of ${\mathrm{Te}}^{127}$ and ${\mathrm{Te}}^{127m}$ have been examined by beta-ray spectrometry and gamma-ray scintillation spectrometry. ${\mathrm{Te}}^{127}$ (9.35\ifmmode\pm\else\textpm\fi{}0.10 hr) decays predominantly (99%) by a beta transition of end-point energy 695\ifmmode\pm\else\textpm\fi{}10 kev to the ground state of ${\mathrm{I}}^{127}$. The remaining 1.0\ifmmode\pm\else\textpm\fi{}0.2% of the decay is accompanied by gamma rays of energies 58.5\ifmmode\pm\else\textpm\fi{}1, 145\ifmmode\pm\else\textpm\fi{}2, 203\ifmmode\pm\else\textpm\fi{}3, 215\ifmmode\pm\else\textpm\fi{}4, 360\ifmmode\pm\else\textpm\fi{}4, and 418\ifmmode\pm\else\textpm\fi{}2 kev. By means of gamma-gamma coincidence measurements, these gamma rays have been fitted into a consistent decay scheme which involves levels in ${\mathrm{I}}^{127}$ at 58.5, 203, and 418 kev. ${\mathrm{Te}}^{127m}$ (105\ifmmode\pm\else\textpm\fi{}2 days), which decays predominantly by the well-known 89-kev isomeric transition, also has a 1.5\ifmmode\pm\else\textpm\fi{}0.5% beta branch which populates the 58.5-kev level in ${\mathrm{I}}^{127}$ and another beta branch of total intensity \ensuremath{\sim}0.013% which is accompanied by a gamma ray of energy 665\ifmmode\pm\else\textpm\fi{}5 kev. Plausible spin and parity assignments for the excited levels of ${\mathrm{I}}^{127}$ are discussed.

Radiations ofMo90and the Isomeric States ofNb90

Gamma-gamma coincidence measurements of the radiations of 5.7-hour Mo 90 showed that the 120- and 250-kev gamma rays previously reported by Diamond were delayed. Further experiments showed the existence of a 24-second isomer of Nb 90 emitting 120-kev gamma rays and a 10 to 20 millisecond isomer emitting 250-kev gamma rays. The transition types were not assigned unambiguously but the 24-second isomer is probably E2 and the 10 to 20 millisecond isomer E3 or M3 in nature. The radiations of the 14.6-hour ground state of Nb 90 were also studied. The 140-kev and 1.14-Mev gamma rays are in coincidence with each other and with annihilation radiation. A prominent 2.2-Mev gamma ray is not in coincidence with annihilation radiation or x-rays. Hence, it must be a delayed transition with ΔI≥3. This is of interest because of the rarity of such transitions in even-even nuclei.