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Specialty Chemistry Forums => Nuclear Chemistry and Radiochemistry Forum => Topic started by: gippgig on May 07, 2014, 03:31:02 AM

Title: GSI confirms 117
Post by: gippgig on May 07, 2014, 03:31:02 AM
DOI: 10.1103/PhysRevLett.112.172501
They also identified 266Lr.
Title: Re: GSI confirms 117
Post by: ik3 on May 07, 2014, 08:46:57 AM
The nucleus 266Lr would be the heaviest β decay nucleus observed so far, supposing the β-stable line of odd-Z nuclei is extrapolated along the 2Z−N=44 line (247Bk, 253Es, 259Md, 265Lr, 271Db and so on). The coincident SF signal of the daughter nucleus 266Rf with a short SF half-life may support the identification of the β decay of 266Lr, similar to the case of 262Lr and its EC daughter 262No with a half-life of 5mesc.
Title: Re: GSI confirms 117
Post by: Dan1195 on May 24, 2014, 05:22:10 PM
RE: SF vs EC/β- decay for 270Db and SF vs β- decay for 266Lr

Based on the limited SF data we have for adjacent nuclei and the knowledge that unpaired nucleons create a hindrance factor of 500-1000 for SF decay it is very probable that we observed the Even-Even daughter fission and not direct fission of 270Db or 266Lr. Lets look at each isotope separately:

266Lr: Only adjacent nucleus with a known SF lifetime is 267Rf at ~1.3 hours based on 2 decays. A hindrance factor of 500 would result in a SF lifetime of >10 days. Much greater than the 11 hour SF activity observed. This is likely β-.

270Db: Only adjacent nucleus with SF decay reported is 271Sg (~6 m SF partial based on 1 SF and 2 α decays).  A ~10 hour SF partial lifetime for 270Db would mean a hindrance factor of ~100 compared to 271Sg. This has a better chance to be direct SF. 
Title: Re: GSI confirms 117
Post by: Dan1195 on June 15, 2014, 10:23:44 AM
This study makes me wonder if potential alpha branching of 268Db was also missed due to the longer lifetime of the nucleus. The longer lifetime may make detection more difficult but at the same time the experiment can be done without the limitations associated with the Berkelium target (i.e. short half-life, handling issues, etc.)