Low Mass Francium and Emanation Isotopes of High AlphaStability
Isotopes of francium with 126 or fewer neutrons have been looked for in bombardments of Th{sup 232} with 350 Mev protons from the 184-inch cyclotron. Fr{sup 212} with an apparent half-life of 19.3 minutes for branching decay by alpha emission (44%) to At{sup 208} and by orbital electron capture (56%) to Em{sup 212} has been found. Em{sup 212} is shown to be a 23-minute alpha-emitter. At{sup 208} decays primarily (99.5%) by orbital electron capture to Po{sup 208}, but shows 0.5% alpha-branching. The francium and emanation isotopes have alpha half-lives completely out of line with the predictions based on the previously known isotopes of these elements. Their high alpha stability is believed to be due to a closed shell of 126 neutrons in analogy to the behavior of elements 83-85. The non-existence of long-lived francium in nature is discussed in the terms of this and other recent work on francium isotopes.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USAEC
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 932808
- Report Number(s):
- UCRL--469; AECU-654
- Country of Publication:
- United States
- Language:
- English
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