Scientists finally detected O-28. It's instability surprised them

[WestMichRad]

https://www.sciencenews.org/article/oxygen-28-instability-surprise-physics

Using a powerful particle accelerator, researchers have spotted an elusive variant of oxygen for the first time. The isotope, oxygen-28, was predicted to be stable thanks to its eight protons and 20 neutrons — “magic” numbers associated with extra stability in atomic nuclei.

Atomic nuclei are made up of protons and neutrons, each of which are thought to occupy their own “shells” — discrete energy levels that are separated by large energy gaps. Atomic nuclei with full outer shells are bound extra tightly, making them very stable. Shells fill up when they hit two, eight, 20, 28, 50, 82 and 126 subatomic particles (SN: 10/9/13).

Finding the isotope took a combination of brute force and experimental elegance. Physicist Yosuke Kondo of the Tokyo Institute of Technology and colleagues used a particle accelerator to smash calcium-48 atoms against a beryllium target. This fragmented the calcium-48 atoms into lighter isotopes, including fluorine-29. Throwing the fluorine-29 against a liquid hydrogen target knocked off a single proton, producing oxygen-28.”

Scientists expected the isotope to be stable, but it isn’t: it sloughs off 4 neutrons in a femtosecond (1E-21 sec). O-28’s surprising instability indicates there’s something we don’t understand about the strong nuclear force, which binds together protons and neutrons in the atomic nucleus.

A little more in the article.

[John1956PA]

1. Wow! O-28 has a neutron excess of 12.

When the O-28 nucleus sheds four neutrons, as the article says that it does in a femtosecond, it has a neutron excess of 8. We can breathe easily knowing that good ole' O-16 is the most plentiful and most stable isotope.

ON EDIT: The correct word "neutrons" was inserted to replace a word which I mistakenly typed in the original version of this reply post.

[Wounded Bear]

2. Neutrons, not electrons...

No electrons in the nucleus.

[John1956PA]

4. Thank you for correcting my misstatement. I am going to edit my post to state . . .

. . . that four neutrons (not electrons as I absent-mindedly stated) are shed in that incredibly short interval of time.

That you for you interesting OP. Best wishes.

[Wounded Bear]

5. Not my OP, but thanks...nt

[eppur_se_muova]

3. I'm baffled as to why this should be surprising -- closed shells can only do so much.

This nuclide still has a HUGE excess of neutrons.

I can only assume this is confusion on the part of a science journalist, who took 'relatively' stable and indefinitely stable -- the canonical usage of the word 'stable' -- to mean the same thing.

Si-28 is the only stable nuclide with A=28; no others should be expected.

https://en.wikipedia.org/wiki/Beta-decay_stable_isobars