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This article is about an undiscovered element. Once it is discovered, this article will be edited with more information.

Untripentium, Utp, is the temporary name for element 135. Isotopes are predicted in the bands Utp 445 to Utp 385, Utp 372 to Utp 353, and Utp 319 to Utp 316. There may be isotopes in the band from the neutron dripline to Utp 446, but it is not possible to predict which ones are possible. Reported half-lives are all less than 1 hr, and most are under 1 sec. Forty-seven isotopes within the bands Utp 445 to Utp 429 and Utp 423 to Utp 392 are predicted to form. All Utp isotopes, predicted or guessed, will last less than 1000 sec after the event which led to their formation.

NUCLEAR PROPERTIES

INFORMATION SOURCES

While studies addressing specific issues have been carried out to very high N(1). and to moderate Z(2), (Z,N) or (Z,A) maps predicting half-lives and decay modes are almost completely limited to the region below Z = 130 and N = 220. There appears to be only one such map which extends beyond that region and is accessible(3).

(Z,N) maps for half-life and decay mode in Ref. 3 extend as high as Z = 175 and N = 333. Half-lives are reported as bands 3 orders of magnitude wide (0.001 - 1 sec, for example), and should be considered accurate only to within +/- orders of magnitude (presumably from band center. (A nuclide reported to be in the 0.001 - 1 sec band should be considered to have a possible half-life between 10^-4.5 sec and 10^1.5 sec.) Decay modes are limited alpha emission, beta emission, proton emission, and fission; and to the principal one for each nuclide. There are areas where two modes (or more) may be important, meaning that small uncertainties is model parameters could have produced different results. It is also possible that cluster decay may become important above the neutron shell closures at N = 228 and 308.

Ref. 3 does have two significant weakness in the way data are presented. Nuclides which are beta-stable are identified by black squares, overwriting decay mode and half-life information. In addition, nuclides having half-lives less than 10^-09 sec are not reported, which obscures the distinction between nuclides having half-lives in the 10^-09 and 10^-14 sec band and nuclear drops whose half-life is under 10^-14 sec.

Above Z around 126, predictions in Ref. 3 may not reach the neutron dripline. This can be an important limitation because the only processes which can form nuclei at more than atoms / star quantity generate very neutron-rich nuclei. It is possible to to make a crude, but conservative (high N) guess for the dripline's location by averaging predicted values for even-N nuclei.{See "The Final Element" (this wiki).} It is also possible to guess at regions of the (Z,N) or (Z,A) plane in which a fission barrier high enough to permit nuclides exists by using a first-order, liquid drop model. {See "Nuclear Guesswork" (this wiki).} Specific numbers are reported for these guesses, not with the expectation that they are accurate, but because they are consistent from element to element. They allow construction of a map which at least hints at where in the (Z,A) plane nuclides may be found.

GUESSED PROPERTIES

A simple liquid-drop picture indicates that Utp 481 to Utp 446 are unlikely to decay by neutron emission and are stable enough against fission to allow beta decay. Between Utp 468 and Utp 446, Ref. 3 probably makes no predictions, but extrapolation from higher Z indicates that it would predict some short-lived, fission-decaying nuclides. Nuclear properties above Utp 445 are highly uncertain, but it is possible that some relatively long-lived, beta-decaying isotopes of Utp are possible. It is possible to state that half-lives longer than 1 sec are implausible between the neutron dripline (nominally Utp 481) and Utp 446.

PREDICTED PROPERTIES

Isotopes in the band Utp 445 - Utp 432 are predicted to decay by beta emission. Since predicted half-lives are in the 10^-06 - 0.001 sec range and beta decay partial half-lives far from stability have a minimum near 0.001 sec(4), that is about where half-lives should lie.

Isotopes in the band Utp 431 - Utp 425 are predicted to decay by fission. It appears to be possible for structure to destabilize a nuclide(5), so the data reported appear to be realistic, Half-lives predicted are in the 10^-06 - 0.001 sec range at the upper end of this band and in the 0.001 - 1 sec range at the lower. Beta emission is probably an important secondary decay mode.

Isotopes in the band Utp 425 - Utp 400 are predicted to decay by beta emission, with half-lives in the 0.001 - 1 sec range.

Odd-N isotopes in the band Utp 399 to Utp 394 are predicted to decay by beta emission, with half-lives in the 0.001 - 1 sec range. Even-N isotopes in this band are predicted to decay by fission. They are also predicted to have half-lives in the 0.001 - 1 sec range, except for Utp 395, which is predicted to have a half-life in the 10^-09 - 10^-06 sec range.

Utp 393 and Utp 391 are predicted to decay by beta emission, with half-lives in the 0.001 - 1 sec range. This prediction seems questionable. Both are even-N nuclides, while the adjacent Utp 392 and Utp 390 - which are odd-N nuclides - have half-lives under 10^-09 sec.

Utp 389 and Utp 388 have half-lives under 10^-09 sec, and presumably decay by fission.

Between Utp 387 and Utp 385, isotopes are predicted to have half-lives in the 0.001 - 1 sec range. Utp 387 is predicted to decay by fission and the others by beta emission.

There is a gap from Utp 384 to Utp 373 in which properties are not reported. These may be short lived nuclides or nuclear drops whose half-life is less than 10^-14 sec. It appears to be the expected destabilized region above N = 228.

Between Utp 372 and Utp 355, all isotopes are predicted to decay by fission. Half-lives increase as A declines from the 10^-09 - 10^-06 sec range (with a few having half-lives under 10^-09 sec) to the 0.001 - 1 sec range at Utp 364 and Utp 363 (for which N = 228), then falling quickly to the 10^-09 - 10^-06 sec range (and below).

Utp 354 and Utp 353 are predicted to have half-lives in the 0.001 - 1 sec range and to decay by alpha emission.

There is a gap from Utp 352 to Utp 320. There may either be nuclides with half-lives under 10^-09 sec or nuclear drops too short-lived to qualify as nuclides in this band.

Utp 319 and Utp 318 are predicted to decay by proton emission with half-lives in the 10^-09 - 10^-06 sec range. Utp 316 is predicted to decay by alpha emission in the same half-life range. Everything else below Utp 320 is either very short lived nuclides or nuclear drops.

OCCURRENCE

FORMATION

Where nuclear drops between the neutron dripline (nominally Utp 481) and Utp 446 can be nuclides, they may form. Heavier isotopes may form directly from disintegrating neutron star material, and the remainder may form via beta decay chains from lower-Z nuclides. Since some of these chains may be terminated by short-lived, fission-decaying nuclides, it is not possible to say which isotopes of Utp in this range can form.

Nearly all nuclear drops in the bands Utp 445 to Utp 391, Utp 387 to Utp 385, Utp 372 to Utp 353, and Utp 319 to Utp 315 are predicted to be nuclides. All are too far from the neutron dripline to form directly. It is possible to simulate the formation of nuclides via decay chains using data from Ref. 3 and assuming an initial distribution close to the neutron dripline. Details of the model are provided in "Nuclear Decay Chains at High A" in this wiki. Per that model, 47 predicted isotopes; Utp 445 to Utp 429, Utp 423 to Utp 397, Utp 395, and Utp 393 to Utp 392; can form.

It is implausible that neutron capture can form any Utp isotope.

PERSISTENCE

All isotopes of Utp are expected to vanish within 1000 sec of the neutron star merger or other event which led to their formation.

ATOMIC PROPERTIES

Electron structure of Utp has been predicted by several sources (see "Extended Periodic Table" in Wikipedia). Up to Z = 137, an atom's nucleus may be regarded as pointlike for the purpose of calculating electron configurations, which means predicted electron structure and behavior can be read with some confidence. Its consensus electron configuration has been predicted to be [Og] 5g9 6f4 8s2 8p21/2.

REFERENCES

1. for example, "Nuclear Energy Density Functionals: What Do We Really Know?"; Aurel Bulgac, Michael McNeil Forbes, and Shi Jin; Researchgate publication 279633220 or arXiv: 1506.09195v1 [nucl-th] 30 Jun 2015.

2. for example "Fission Mechanism of Exotic Nuclei"; Research Group for Heavy Element Nuclear Science; http://asrc.jaea.go.jp/soshiki/gr/HENS-gr/np/research/pageFission_e.html.; 17 Sept 17.

3. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011.

4. "Nuclear Properties for Astrophysical Applications"; P. Moller & J. R. Nix; Los Alamos National Laboratory website; search by "LANL, T2", then "Nuclear Properties for Astrophysical Applications".

5. "Magic Numbers of Ultraheavy Nuclei"; Vitali Denisov; Physics of Atomic Nuclei; researchgate.net/publications/225734594; July 2005.

6. Other references are found in the wiki articles cited.

(07-04-20)

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