[gippgig]

A recent paper (Physical Review C 77 064320) analyses the reported properties of ²⁶⁵Sg. 2 different isomers of this nuclide were identified: ²⁶⁵Sg^a, which has a half-life of 9 s and mainly decays (8.85 MeV a) to ²⁶¹Rf^a (68 s a 8.28 MeV), & ²⁶⁵Sg^b, with a 16 s half-life that mainly decays (8.69 MeV a) to ²⁶¹Rf^b (3 s  91% SF 9% a 8.51 MeV). ²⁶⁹Hs primarily decays to ²⁶⁵Sg^b while the ²⁴⁸Cm(²²Ne,5n) reaction produces both isomers. As with ²⁶¹Rf, it is not clear which is the ground state. This paper also raises the same issue about ²⁶²Rf I previously mentioned (see "Transactinide decay chain misidentification" entry).

[Dan1195]

I saw this on an online PPT presentation. The presence of isomers has complicated the efforts to correctly identify and confirm some decay chains, the ²⁶⁹Hs chain in particular. I had an earlier post which looked at the studies which identified ²⁶²Rf as having a 2 s half-life. Phys. Rev. Lett. 73, 624-627 (1994) and Phys. Rev. C 57, 1648-1655 (1998) based the ID of it from ²⁶⁶Sg alpha decay, which was very likely from ²⁶⁵Sg as it is now known that ²⁶⁶Sg decays by SF with a shorter lifetime. One other study claimed direct production, altough I personally only consider that a tentative assignment.

[gippgig]

The current paper refers to a previous study (PRC 53 2893; I have not read this yet) that assigned a 2.1 s half-life to ²⁶²Rf on the basis of direct production in the ²⁴⁴Pu(²²Ne,4n) reaction and states that "An analysis of the reported excitation function shows a much better agreement with the HIVAP prediction for the ²⁴⁴Pu(²²Ne,5n)²⁶¹Rf than for the ²⁴⁴Pu(²²Ne,4n)²⁶²Rf reaction...".

[Dan1195]

Prior to that study, Phys. Rev. C 31, 1801-1815 (1985) reported a 47 ms SF emitter and tentatively assigned it to ²⁶²Rf, but have not seen this verified with another study. Unfortunately observing this nuclide as a decay product is problematic, as 100+ decays of ²⁶⁶Sg would likely be needed to observed alpha radioactivity from this nuclide based on region systematics. ^262Rf is also the EC daughter of ^262Db, but then you have the issue of distinguishing the EC from the SF as far as lifetime measurements go.