October 15, 2019, 08:01:54 PM
Forum Rules: Read This Before Posting


Topic: The original Dubna "element 114" decay chain  (Read 23301 times)

0 Members and 1 Guest are viewing this topic.

Offline Dan1195

  • Regular Member
  • ***
  • Posts: 75
  • Mole Snacks: +2/-0
The original Dubna "element 114" decay chain
« on: January 27, 2009, 08:55:40 PM »
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.
« Last Edit: January 27, 2009, 09:29:03 PM by Dan1195 »

Offline Mitch

  • General Chemist
  • Administrator
  • Sr. Member
  • *
  • Posts: 5290
  • Mole Snacks: +376/-2
  • Gender: Male
  • "I bring you peace." -Mr. Burns
    • Chemistry Blog
Re: The original Dubna "element 114" decay chain
« Reply #1 on: January 27, 2009, 10:43:19 PM »
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? :)
Most Common Suggestions I Make on the Forums.
1. Start by writing a balanced chemical equation.
2. Don't confuse thermodynamic stability with chemical reactivity.
3. Forum Supports LaTex

Offline gippgig

  • Full Member
  • ****
  • Posts: 139
  • Mole Snacks: +8/-2
Re: The original Dubna "element 114" decay chain
« Reply #2 on: January 28, 2009, 04:37:44 PM »
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.

Offline Grejak

  • Chemist
  • Regular Member
  • *
  • Posts: 43
  • Mole Snacks: +5/-0
  • Gender: Female
Re: The original Dubna "element 114" decay chain
« Reply #3 on: February 11, 2009, 07:08:46 AM »

Offline Dan1195

  • Regular Member
  • ***
  • Posts: 75
  • Mole Snacks: +2/-0
Re: The original Dubna "element 114" decay chain
« Reply #4 on: March 26, 2010, 05:13:41 PM »
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.
« Last Edit: March 26, 2010, 05:38:57 PM by Dan1195 »

Offline Dan1195

  • Regular Member
  • ***
  • Posts: 75
  • Mole Snacks: +2/-0
Re: The original Dubna "element 114" decay chain
« Reply #5 on: April 21, 2010, 05:26:28 PM »
Hmm...upon further review of the element 117 decay chains, 289113 doesn't make too much sense either.

From Dubna:

285113 : t1/2=5.5 s Qa=9740 keV
286113 : t1/2=~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: t1/2=66 s Qa~9630-9700 keV

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

Offline Dan1195

  • Regular Member
  • ***
  • Posts: 75
  • Mole Snacks: +2/-0
Re: The original Dubna "element 114" decay chain
« Reply #6 on: September 01, 2013, 06:30:44 AM »
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.
« Last Edit: September 01, 2013, 06:42:51 AM by Dan1195 »

Offline gippgig

  • Full Member
  • ****
  • Posts: 139
  • Mole Snacks: +8/-2
Re: The original Dubna "element 114" decay chain
« Reply #7 on: September 02, 2013, 09:22:49 PM »
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!

Offline Dan1195

  • Regular Member
  • ***
  • Posts: 75
  • Mole Snacks: +2/-0
Re: The original Dubna "element 114" decay chain
« Reply #8 on: September 18, 2014, 09:12:31 PM »
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

Offline Nathan K

  • Very New Member
  • *
  • Posts: 1
  • Mole Snacks: +0/-0
Re: The original Dubna "element 114" decay chain
« Reply #9 on: December 08, 2014, 08:39:53 PM »
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.

Offline ik3

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: The original Dubna "element 114" decay chain
« Reply #10 on: December 09, 2014, 10:32:32 AM »
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)

Sponsored Links