Here's the paper.[1] No paywall this way; U.S. Government funded research. The paper claims an associated Github repository but there is no obvious link. There's no imagery in the paper, just the development of the math. So this may or may not help much.

[1] https://www.osti.gov/pages/servlets/purl/3001752

Weird that I couldn't find the paper on arXiv: in my field I just google the title prefixed with "arXiv" and it pops up.

Some earlier articles by the same authors are there though (e.g. https://arxiv.org/abs/2310.06106), does the journal of chemical physics prohibit arXiv posting or is the norm just different in that field?

I think the source code is here? https://github.com/pinheirothiagoj/NMR_Molecular_Eigenmodes_...