Discontinuities in nuclear masses

[ptalou]

Describe the bug

Nuclear masses are pulled from the 2012 Audi-Wapstra table. Discontinuities appear, as reported by Mumpower and Jaffke, when theoretical masses are used when experimental ones are not available.

To Reproduce

need to check with Mumpower & Jaffke

Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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