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Extinct isotopes of superheavy elements
are isotopes of
superheavy elements
whose
half-lives
were too short to have lasted through the
formation of the Solar System
,
[1]
and because they are not replenished by natural processes, can nowadays only be found as their
decay products
(from
alpha decay
,
cluster decay
or
spontaneous fission
) trapped within sediment and meteorite samples dating billions of years ago.
Carbonaceous chondrite fission xenon
[
edit
]
Carbonaceous chondrite fission
xenon
(CCF Xe), are a collection of different
isotopes of xenon
that were thought to have arisen from the decay of a superheavy element within the
island of stability
. Early studies proposed that the half life of the theoretical progenitor of CCF Xe to be on the order of 10
8
years.
[2]
A later attempt at characterization of the progenitor in 1975 by Edward Anders, a professor of chemistry at the University of Chicago, and colleague John Larimer suggested a heat of vaporization of 54 kJ/mol and a boiling point of 2500K for the element and, based on estimated accretion temperatures, they also proposed elements 111 and 115 (today named
roentgenium
and
moscovium
) as the most likely candidates assuming the element condensed in pure form.
[3]
Allende meteorite
[
edit
]
Anders went on to study samples of the
Allende meteorite
, the largest
carbonaceous chondrite
ever found on Earth. Results of these studies suggested elements 111?115 (today
roentgenium
,
copernicium
,
nihonium
,
flerovium
, and
moscovium
)
[4]
as the most likely candidates for the progenitor of CCF Xe. These studies also proposed that the progenitor condensed as an iron chromium sulfide.
[5]
This was later called into question as iron chromium sulfide is very rare with a relative abundance of 0.4%.
[6]
Evidence against carbonaceous fission xenon
[
edit
]
By the 1980s, CCF Xe actually being the product of fission was doubtful, and the alternate theory that it had arisen from
r-process
(neutron capture)
nucleosynthesis
gained more ground.
[7]
Researchers looked at the isotopic anomalies in nearby elements
samarium
,
neodymium
, and
barium
, and compared to the amount of xenon. Whether CCF Xe was produced by nucleosynthesis or fission, comparable amounts of barium-135 should be produced.
[6]
When researchers compared the experimental data to predicted amounts of Barium following each model, neither model came close to predicting the anomalies correctly, leading to Lewis et al. calling the experiment an "embarrassment" for both models.
[
citation needed
]
However, in the case of nucleosynthesis, it is possible that
samarium
,
neodymium
, and
barium
were separated from Xe by prior condensation in the supernova shell or plasma processes.
[6]
Based on this data it was deemed unlikely that CCF Xe had actually arose from fission.
References
[
edit
]
- ^
Turner, Grenville; Harrison, T. Mark; Holland, Greg; Mojzsis, Stephen J.; Gilmour, Jamie (2004-01-01). "Extinct
244
Pu in Ancient Zircons".
Science
.
306
(5693): 89?91.
Bibcode
:
2004Sci...306...89T
.
doi
:
10.1126/science.1101014
.
JSTOR
3839259
.
PMID
15459384
.
S2CID
11625563
.
- ^
Schramm, David N. (1971-09-24). "Implied Superheavy Element Decay Lifetime from Meteorites".
Nature
.
233
(5317): 258?260.
Bibcode
:
1971Natur.233..258S
.
doi
:
10.1038/233258a0
.
PMID
16063318
.
S2CID
4171749
.
- ^
Anders, Edward; Larimer, John W. (1972-01-01). "Extinct Superheavy Element in Meteorites: Attempted Characterization".
Science
.
175
(4025): 981?983.
Bibcode
:
1972Sci...175..981A
.
doi
:
10.1126/science.175.4025.981
.
JSTOR
1732722
.
PMID
17791931
.
S2CID
24652899
.
- ^
Anders, Edward; Lewis, R.S. (1981-03-01). "XE129 and the Origin of CCF Xenon in Meteorites".
LUNAR AND PLANETARY SCIENCE XII, P. 616-618. Abstract.
: 616.
Bibcode
:
1981LPI....12..616L
.
{{
cite journal
}}
: CS1 maint: multiple names: authors list (
link
)
- ^
Anders, Edward; Higuchi, H.; Gros, Jacques; Takahashi, H.; Morgan, John W. (1975-01-01). "Extinct Superheavy Element in the Allende Meteorite".
Science
.
190
(4221): 1262?1271.
Bibcode
:
1975Sci...190.1262A
.
doi
:
10.1126/science.190.4221.1262
.
JSTOR
1741804
.
S2CID
96924953
.
- ^
a
b
c
Lewis, R. S.; Anders, E.; Shimamura, T.; Lugmair, G. W. (1983-01-01). "Barium Isotopes in Allende Meteorite: Evidence against an Extinct Superheavy Element".
Science
.
222
(4627): 1013?1015.
Bibcode
:
1983Sci...222.1013L
.
doi
:
10.1126/science.222.4627.1013
.
JSTOR
1691282
.
PMID
17776244
.
S2CID
532158
.
- ^
Black, David C. (1975-02-06). "Alternative hypothesis for the origin of CCF xenon".
Nature
.
253
(5491): 417?419.
Bibcode
:
1975Natur.253..417B
.
doi
:
10.1038/253417a0
.
S2CID
4293499
.