Superheavy element half-life measurements push back the limits of stability | Hacker News Reader

Superheavy element half-life measurements push back the limits of stability

chemistryworld.com

22 pointsbookofjoe11 comments

My take away from this article is that the super heavy element Rutherfordium can barely be agreed to even exist outside of a theoretical sense.

Rutherfordium has relatively stable isotopes (up to 48 min) [1] and is definitely agreed to exist. This article is about extremely neutron-deficient isotopes and their excited states.

1. https://en.wikipedia.org/wiki/Rutherfordium

There are two forces fighting with each other: Many protons repel each other with their positve electric charge. But they also attract each other with their strong force. It's complicated but if you simplify you could say too large nuclei tend not to hold together.

If you add electric neutral neutrons you have more strong force but the electrical repulsion doesn't increase. So if you have more neutrons, you might have larger nuclei.

They measured what happens if some element's isotope has too few neutrons. They were surprised about the extremely short half-times. From that they estimated on the opposite side (again simplifying here!) that very large nuclei with a lot of neutrons could be stabler than known up to today.

So: on one side (few neutrons) extremely unstable, so on the other side (more neutrons) stabler than expected?

That's what I understood from the article. I have no idea.

Close, but not quite. The general tendency for large nuclei to be less stable is correct, but for any given size, there is something of a optimum proton/neutron ratio that is most stable, and either adding or removing neutrons will reduce the half-life (minus various complications involving magic numbers etc.). At the very neutron-rich end, isotopes tend to spontaneously and rapidly emit the excess neutrons, and at the very neutron-poor end they will spontaneously shed protons to stabilize themselves. If you map these boundaries on the table of nuclides, you get the so-called neutron and proton driplines, respectively, which delineate the isotopes that, as GGP put it, can be reasonably agreed to exist. If you are interested in this stuff, [1] is a decent overview.

This paricular article is about mapping out isotopes close to the proton-drip-line in a heavy synthetic element, with the particular result that excited states can be more long-lived than the ground state of the isotope. This again is nothing particularly new. Generally excited states are short-lived, but there are many known examples of inversion, with the most extreme being a rare, naturally occurring, isotope of Tantalum: Ta-180m. The ground state Ta-180 has a half-life of 8 minutes, while the excited state is de facto stable, with a still unknown half-life in excess of 3*10^17 years [2].

1. https://en.wikipedia.org/wiki/Island_of_stability

2. https://en.wikipedia.org/wiki/Isotopes_of_tantalum#Tantalum-...

Ah ok thank you for clarifying

> bombarding lead with a beam of titanium-50 accelerated to 10% the speed of light

Please forgive the poor understanding, but isn't titanium non-magnetic? How does one accelerate titanium?

They are talking about titanium ions.

I've always wondered how this actually works. Do you have to vaporize it first? How do you actually get titanium to become free-floating (?) ions?

I believe it is vaporized then (partially) ionized by bombardment with electrons.

oh, right. Thank you for helping a bear with very little brain.

Bob Lazar knows better...

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