Isotope data overhaul

[jkshenton]

The isotope data (nuclear spin, quadrupole moments etc.) need to be checked/outsourced to an external library with clearer provenance. Perhaps https://github.com/lmmentel/mendeleev ?

• Some existing data seems to be wrong: For example, the quadrupole moment on 19F is zero in its ground state, not -94.2 mb as in the https://github.com/CCP-NC/soprano/blob/master/soprano/data/nmrdata.json file... That number appears to be for the 5/2 spin excited state (197 keV above the ground state).

• Data on lots of isotopes is missing. e.g. for 8Li, a commonly used isotope in beta-NMR.

[jryates]

The quadrupole moments are updated from time to time. I think the current recommended set at from 2017 https://www.tandfonline.com/doi/full/10.1080/00268976.2018.1426131 And before that is was 2008 There has sometimes been some rather significant changes from set to set.

But I do think that having this - and some other key NMR data in a good public format would be a good thing.

[jkshenton]

There are some nice .csv files available here: https://www-nds.iaea.org/nuclearmoments/index.html based on a 2021 table by N. J. Stone (says it's also in consultation with the author of the paper you cite, Pekka Pyykkö). These have been parsed and made available in the https://github.com/lmmentel/mendeleev library -- I'm thinking to use that library as a drop-in replacement for isotope data handling. What do you think @jryates?

[jryates]

Yes, that makes sense.