Island of Stability - How would we detect it?

[tw60407]

From my general understanding of physics we detect the creation of elements above 92 protons by the decay of the larger element into lighter elements. Since we use particle accelerators to create these heavier elements if we did create a completely stable isotope of element 118 for example... would we know? Is it possible that there is a bunch of it sitting at the bottom of the particle accelerators just waiting to be swept up? I am half joking on the sweeping aspect but do we have means of detecting for a completely stable element produced during high energy particle collisions?

 

[mfb]

If the collision directly produces a stable nuclide, it would be very hard to detect that. If it produces something that decays to this stable nuclide (including gamma decays), then we can find those decays. It is unlikely that the island of stability has any stable isotopes, however.

If there is a good argument to expect stable superheavy nuclei you could add a sensitive mass spectrometer to detect it (the rate of events will go down as you are now limited to some velocity range).

 

[Janus]

It is unlikely that the island of stability has any stable isotopes, however.

Right, the term "island of stability" is a bit misleading, "island of relative stability" might be more accurate.

 

[Vanadium 50]

"island of relative stability" might be more accurate.

True that.

If there were stable nuclei, we would also probably have found them in moon dust or meteorites. They would have been exposed to cosmic ray nuclei for billions of years. (This is why people look for them in these places)

 

[ShayanJ]

If the collision directly produces a stable nuclide, it would be very hard to detect that.

If you can't detect some of the particles produced after the collision, can't you use conservation laws to deduce that they were produced?

 

[mfb]

If you can't detect some of the particles produced after the collision, can't you use conservation laws to deduce that they were produced?

In a collider you could do that, in a fixed-target experiment some energy gets lost in the target, and you don't have the capabilities of tracking every single interaction - you need a very high event rate (~10¹⁹ collisions) to have a chance to get some atoms.

 

[snorkack]

If you did not have primordial Th-232 (and U-235 and -238), would there be any plausible way to produce Th-232 from Pb or Bi?

 

[mfb]

Tricky, as the neutron to proton ratio is hard to reproduce with the stable elements. Irradiating stuff with neutrons could help, but without fissile materials we would not have affordable strong neutron sources either.

 

[snorkack]

Tricky, as the neutron to proton ratio is hard to reproduce with the stable elements. Irradiating stuff with neutrons could help, but without fissile materials we would not have affordable strong neutron sources either.

And slow neutron capture terminates at bismuth 209, because Po-210 is alpha radioactive with 138 day half-life...
does not stop Th-232 with 14 milliards year half-life from existing.

As far as berkelium, all elements have known neutron-rich isotopes that undergo beta decay.
But starting from californium, the heaviest known isotopes do not undergo beta decay. They decay by alpha, fission and electron capture.
Therefore, for elements beginning with californium, there is an obvious possibility of existence of neutron-rich isotopes as yet undiscovered, and longer-lived than the so far discovered neutron-poor isotopes.

If there were isotopes with half-life of hundreds of millions of years, you might expect small yields to have ended up on Earth as primordial radioisotopes. However, for half-lives up to tens of millions of years, small yields produced in nature would not be extant, and small yields produced in laboratories would not announce their presence by decaying.

 

[mfb]

But starting from californium, the heaviest known isotopes do not undergo beta decay.

²⁵³Cf and ²⁵⁵Cf have beta- as dominant decay channel, 254 and 256 have a rare double beta decay.
^254mEs, ²⁵⁵Es, ²⁵⁶Es, ^256mEs, ²⁵⁷Es have beta- as dominant decay channel.
Fermium has no beta- decays observed so far.
²⁵⁸Md, ^258mMd, ²⁶⁰Md have observed beta decays.

Beyond that I didn't find beta- decays, but note that beta+ decays become rare as well. Alpha and spontaneous fission just get too fast, so they dominate.

Calculations indicate that the heaviest produced isotopes are more on the proton-rich side, but that's unavoidable - they are produced in collisions of lighter isotopes which don't have the ideal neutron to proton ratio for the superheavy elements.