Strong evidence for new light isotope of nitrogen

The arxiv version of the paper says:

the decay widths of the low-lying states increase, eventually melting into an unresolvable continuum as their lifetimes become commensurate with typical reaction and single-particle timescales. Here, the very notion of the nuclear state becomes questionable as the timescales are too short to talk about the existence of a nucleus. Indeed as dis- cussed in Ref. [9], if a collection of nucleons survives for less than about 10−22 s, it should not be considered a nucleus.

https://arxiv.org/abs/2309.15180

It's call isospin https://en.wikipedia.org/wiki/Isospin Its a symmetry. The idea is that you can imagine that there is a magical switch outside the universe that can transform all protons into neutrons and viceversa [1], and if you activate the switch nobody would notice. It's a broken symmetry, so activating the switch will be noticed, but it's a good enough approximation for small nuclei. For example the nuclei in H3 and He3 are very similar. I don't remember any remarks about nuclei with 5 nucleons, but I'm not an expert in that area, so I guess it's known. (It's a nice observation!)

The idea is that isospin can be used to classify nuclei and composite particles and collisions, and you can use isospin to prove that some collisions are imposible or that two collisions have (almost) the same probability.

In my university is one of the last courses of a Physics degree. The calculations of isospin are quite easy, just multiply some 2x2 matrices. Understanding which marices to multiply and how to interpret the result is more difficult. Understanding that this is a good approximation of the universe (for small nuclei) and believing that the profesor explaining it is not a crackpot takes a few years of physics preparation.

[1] It's more complicated, instead of a switch, it's like a dial you can rotate and transform a proton into a 80% proton and 20% neutron or any combination you like. And actually, it's more complicated, there are more restrictions and the transformation must be unitary.

And I had to look this up. The most stable form of Nitrogen is N14, so I guess it normally has 7 neutrons and N9 is produced when N14 sheds 5 neutrons. Other isotopes are N13 (rare, short lived) and N15 (0.4% of all nitrogen, stable).

If I read the article correctly, N-9 is actually a helium nucleus (or alpha particle) with some protons that happen to stick around near to it for fractions of a second that are too short to comprehend - but apparently they detected that a single proton decides to leave first (-> C-8), then one pair (-> Be-6) and finally another (-> He-4).

Are you basing this on anything more than pop science reckons?

No, you can't. Many combinations do not merge at a nucleus at all.

I struggled to come up with a fair definition of nucleus. Indeed, some of these nucleon soups are more like mist than anything. And so my definition is: if a photon can traverse the width of the "nucleus" and the nucleus still exists by the time it gets to the other side, it's a nucleus. If it cannot hold together even that long, it doesn't count.

If for you "horrendously powerful nuclear explosion" is synonymous with "lifting", then, by all means.

This is a crazily unstable isotope that really doesn't want to exist ;)