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Levels in Pb202and Tl202populated from 3.62-h Pb202m

Nuclear Physics
Publication Date
DOI: 10.1016/0029-5582(57)90017-2


Abstract Using beta spectroscopic techniques, conversion electrons of transitions following the decay of 3.62-h Pb 202m have been investigated. The previously suggested level sequence in Pb 202 is unambiguously supported by our results: 0+ (0 keV), 2+ (961.4 keV), 4+ (1383.5 keV), 5− (2041.1 keV) and 9− (2170.7 keV). From the 9− state two gamma rays of multipolarity E4 (129.3 keV) and E5 (787.2 keV) are emitted. In addition, a very weak E5 transition of energy 547.2 keV between the 9− state and a second 4+ state (1623.8 keV) was observed, as well as an Ml transition of energy 240.3 keV between the two 4+ states. The succession of the 422.1 keV and 961.4 keV transitions was determined by comparing their relative intensities in the decay of Pb 202m and Bi 202. Except for the 5− level, the similarity between levels in Pb 202 and Pb 204 is very striking. The 9− state in Pb 202 was found to be deexcited also by electron capture (9.7%) to levels in Tl 202. The following level sequence is suggested for the Tl branch: 2− (0 keV), 4− (490.4 keV), 7+ (950.2 keV), 6+ (1099.1 keV) and 8+ (1340.1 keV). The 8+ state is deexcited by an Ml transition of energy 389.9 keV, and also by a 241.1 keV E2 transition followed by a 148.9 keV Ml transition. The isomeric 7+ state is deexcited by a 459.8 keV E3 transition and a 490.4 keV E2 transition in cascade. The succession of the 389.9, 459.8 and 490.4 keV transitions is suggested from coincidence measurements. A gamma ray of energy 335.6 keV and multipolarity Ml (?) may be emmited from an 8+ or 9+ (1675.7 keV) level to the 8+ (1340.1 keV) level. In addition, some weak conversion lines were found, to which no definite assignment could be given.

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