[Dan1195]

It has become apparent that many decay chains attributed to specific transactinide isotopes have been initially misidentified in recent years. Many of the early russian "Hot Fusion" element 114 chains were one mass number off. The same has apparently happened with Sg-256-266 and Hs-269-270. Looks like a variety of factors are causing this:

1. Lack of known nuclide connections.

At a certain point, it will be impossible to ever connect new isotopes to already known ones due to SF decay of Rf and/or the instability of nuclides wth ~170 neutrons to fission. So assignments will have to be based on excitaton functions, data patterns, and SF and alpha systematics and comparision with data to existing predictions of decay properties.

2. Lack of data.

Production rates are so low you can sometimes get 2-3 atoms after weeks of an experiment. Unless two decay modes heavily compete with each other you only see the main mode. (i.e. you probably wont see a 5% fission branch when observation 3 decays.) You could also get a "lucky" decay involving a short or long lifetime or unusual decay mode skewing the data set with such a small sample.

Many decay chains are still missing in between the "Cold Fusion" and "Hot Fusion" production areas. With the N=162 deformed shell enclosure occuring in this area each chain should have clearly distinct properties. Only with all these missing chains filled in can we really have a very high confidence that chains are being assigned correctly.

3. Isomerism

This has caused problems for a few years with regard to the verificition of the GSI element 112 data. Rf-261 is now known to have an isomeric state. Isomerism now appears more prevalent in transactide elements with with actinides (exlcuding fission isomers). Just one more issue to deal  with when trying to verify decay properties.

Ultimately more data solves this problem, but low production rates can leave questions that take a while to be answered.

[gippgig]

This raises a question about ²⁶²Rf. This isotope was originally identified as an ~50ms SF activity. It was then revised to a 1.2s half-life (still SF of course) on the basis of its production as a daughter of the newly identified ²⁶⁶Sg and some previous evidence for an activity with this lifetime. However, what was thought to be ²⁶⁶Sg has been reassigned to ²⁶⁵Sg as mentioned above. So, should ²⁶²Rf be unrevised back to a 50ms half-life?

[Dan1195]

The currently accepted ²⁶²Rf half-life of 2.3 s is based on three sources. Two of them were from the assumed alpha decay of ²⁶⁶Sg. The other was from the reaction ²⁴⁴Pu(²²Ne,4n).

The data from the alpha decay daughters is very likely with the SF emitting isomer of ²⁶¹Rf, which has a very similar half-life. The presence of an isomer in the even-even nucleus ²⁶⁶Sg (likely a K-isomer if it existed) with lifetime and alpha particle energy so close to ²⁶⁵Sg is so unlikely it can be discounted.

Determination of mass based on energy excess of compouned nucleus alone is not always accurate. The latest data makes it even more unclear. Not only is the half-life close to the ²⁶¹Rf isomer. But one decay chain assigned to ²⁷¹Sg ends with the 8 s SF decay of ²⁶³Rf. One atom does not give us enough statistics here. This 8 s value is itself in conflict with the 10 minute lifetime previously given to ²⁶³Rf based on study of ²⁶³Db EC decay. More isomerism? Not enough data here yet it appears.