[Dan1195]

Back in 1999 Dubna make the inital claim of discovery for element 114 with the following decay chain 30.4 s (9.71 MeV alpha)->15.4 m (8.67 MeV alpha)->1.6 m (8.83 MeV alpha)->16.5 m (fission). This chain as initially attributed to ²⁸⁹114 at its decendants, but further experiements detemined that assignment to be in error. A LLNL report https://e-reports-ext.llnl.gov/pdf/302186.pdf which analyed the ²⁴⁸Cm(⁴⁸Ca,4n) experiment in 2000 also found a decay chain (SF event 2 in the paper) which is very similar to the original 1999 chain. Note that all chains in the paper assigned to ²⁸⁸114 have since been re-assigned ot ²⁸⁹114.

Assuming these two decay chains are real, the question is what do they belong to? Dubna suggested ²⁹⁰114, however, viability of the 2n channel aside, I have problems with this assignment as it gives a rather long SF half-life to the termination Even-Even nuclide ²⁷⁸Hs. N=170 is now known to be a location of low fission barrier in between the N=162 deformed shell and the N=184 spherical shell enclosure. The 820 microsecond ²⁸²112 confirms this.

Another possibility floated is these nuclides all being isomers. However with all lifetimes of those two chains somewhat longer with somewhat less alpha energy than the ²⁸⁹114 and decendant ground states, the possibility of three successive isomers in a decay chain all with longer lifetimes and slightly lower alpha energy is highly unlikely.

There is one possible solution I can think of: ²⁸⁹114 has a small EC branch and the alphas observed are from ²⁸⁹113  and decendants. The chain terminates at ²⁷⁷Bh (straight SF with no EC in between as this nucleus is expected to be beta-stable or very close to it.). Note that ²⁸⁹113 itself may have a significant EC branch. However it may EC all the way to a nucleus with a lifetime too long to be detected via SF/alpha in the experiment. So any ²⁸⁹114>EC>EC chains would not be picked up.

[Mitch]

Would this be a good time to say we saw a 114 event at LBL from Ca-48 on Pu-242 a couple days ago?

[gippgig]

That's the best explanation I've seen yet. A less likely possibility is (⁴⁸Ca,p2n) producing ²⁸⁹113 directly. It's odd that the first alpha was apparently missed in the 116 experiment but stranger things have happened. Note that the (⁴⁸Ca,2n) reaction is certainly plausible since it was seen in the ²⁴⁵Cm(⁴⁸Ca,xn) experiment.

[Grejak]

[Dan1195]

Thought I would revisit these two decay chains now that additional data in this region has appeared. I think the ²⁹⁰114 possibility can be discarded for the following reasons:

Half-life jumps too quick from ²⁸⁹114 and ²⁸⁵Cn

Jumps from 2.1 s->66 s and 29 s->8.9 m. respectively, not in line with trends for these elements. Also, ²⁸⁶Cn likely has a SF partial half life of ~10 s based on trends.

Why Would ²⁸²DS decay mostly by Alpha? ²⁸¹Ds is mostly SF.

²⁸⁹113 is still quite possible. With termination at the N=170 isotone as was observed in the ²⁹³117 chains.

[Dan1195]

Hmm...upon further review of the element 117 decay chains, ²⁸⁹113 doesn't make too much sense either.

From Dubna:

²⁸⁵113 : t_1/2=5.5 s Qa=9740 keV
²⁸⁶113 : t^1/2=~20 s Qa=9630 keV

If both chains observed are indeed from the same nuclide then for the chain initially assigned to ²⁸⁹114 by Dubna: t^1/2=66 s Qa~9630-9700 keV

One would expect ²⁸⁹113 to have a lower Qa..Anyways...all speculation without additional data.

[Dan1195]

Was just thinking about other possibilities for this, then realized it didn't work. Guess this isn't resolvable without more data. Within the next few years new facilities should be coming online to allow to better SHE production rates needed to better detect narrow decay pathways.

[gippgig]

Someone should definitely try a long run of the ²⁴⁸Cm + ⁴⁸Ca reaction at low energy both to look for another example of this decay chain (whether the hypothetical missed first decay appeared or not would be very informative) & to search for the (⁴⁸Ca,2n) product. I don't think the 1n reaction is a plausible possibility, but out of idle curiosity what is the predicted decay chain for ²⁹⁵Lv?
Getting back to the Washington Post newspaper, the second place winner for the Style Invitational Week 1032 contest (Sept. 1) "in which we asked for "hidden messages" in public monuments, artworks and other cultural icons" was: Uranium-Nickel-Tellurium-Darmstadtium-Tantalum-Tellurium-Sulfur-Oxygen-Fluorine-Americium-Erbium-Iodine-Calcium! That's UNiTeDsTaTeSOFAmErICa, clearly the formula for the most dangerous, volatile compound in the world. - Mahmoud Ahmadinejad, Iodine-Radium-Nitrogen (Kevin Dopart, Washington). So there is a use for darmstadtium!

[Dan1195]

I think a long run of the ²⁴⁸Cm + ⁴⁸Ca reaction once upgraded facilities come on-line would have another potential benefit: Searching for narrow EC branching toward the center of the stability island. Note that while Odd-Odd nuclei have the highest EC decay probability, they aren't that useful for this goal. ²⁸²Rg has the highest observed alpha lifetime for a primarily α-decaying nuclide above the N=170 fission valley (~90 seconds) and likely has decent probably to EC>²⁸²Ds. Problem is ²⁸²Ds likely decays by SF with <1 second lifetime based on ²⁸⁴Cn and ²⁸⁶Fl data. Also production this decay product requires a Bk target and the limitations associated with it. ²⁸⁵Cn would seem to offer the best chance reach the immediate vicinity in that manner via ²⁸⁵Cn>EC>²⁸⁵Rg>EC>²⁸⁵Ds. Of course EC generally cannot be observed directly and potential long daughter lifetimes will present identification challenges

[Nathan K]

I believe that the original "element 114" decay chain and the similar decay chain observed in the 248Cm+48Ca reaction starts at ununtrium-288, via the p3n exit channel of 244Pu+48Ca and 248Cm+48Ca reactions. Dubna's assignment of the terminal fission, hassium-277 with a lifetime of 16.5 minutes, has since been oberved to fission with a half-life of several milliseconds. I believe that the long-lived terminal fission belongs to bohrium-276, which is in the same fission valley as the millisecond hassium-277. I extrapolated α half-lives to the nuclides ununtrium-288, roentgenium-284, and meitnerium-280 and these extrapolated half-lives match surprisingly well. For example, the ratio between the half-lives of ununtrium-284 and ununtrium-286 is approximately 10, and the ratio of half-lives between neighboring flerovium-287 and flerovium-289 is about 5. Therefore, multiplying the mean of these ratios by the half-life of ununtrium-286 yields the extrapolated α half-life of about 75 seconds or so, which is surprisingly close to the aggregate half-life of the original element 114 event at Dubna and the first detected member of the odd chain observed in the 248Cm+48Ca reaction.
I have been doubtful of the parallel isomer chain myself, but the ununtrium-288 assignment makes perfect sense. The only problem is explaining the yield of the 244Pu(48Ca,p3n)288113 and 248Cm(48Ca,p3n)292115 reactions.

[ik3]

I have just remembered my previous post in 2011. Here, let’s quote a paragraph as below. The case x=3 (N-Z=62) just corresponds to your assignment of the first and original Dubna “element-114” chain, which would be terminated by the spontaneous fission of ²⁷⁶Bh. A detailed prediction of the decay properties of the x=4 (N-Z=61) chain was found in an article about a hypothesis of narrow pathway to the Island of Stability by Zagrebaev et al. This decay chain was predicted to be terminated by the spontaneous fission of ²⁷⁹Mt within a second. For the case x=2 (N-Z=63), no detailed prediction seems to be existed, however, the decay chain would be terminated by ²⁸¹Mt within several minutes with based on the systematics of neighbor nuclei.

[Quoted from my previous post]
Furthermore, the unknown neutron-rich odd-Z nuclei with N-Z=61 to 63 would be synthesized by the p4n to p2n channel as follows. The cross-sections of these reactions are expected to be about 100 fb based on the cross-section ratio between the pxn and the xn channel of the ²⁴⁸Cm + ¹⁸O reactions. These neutron-rich decay chains will be terminated by the spontaneous fission of Bh and Mt nuclei around N=170, and these neutron-rich nuclei are located at near the β-stability line. It is noted no β-stable nuclei are known above Z=105 (Db).
N-Z=61, 62, 63: ²⁴⁸Cm(⁴⁸Ca, pxn) ^291-293Uup (x=2~4)