Nonlinear Zeeman shift #4
Description
Originally I wanted ZLevels arbitrary lambda function etc to encompass any nonlinearity in the Zeeman shift. I couldn't get it to work with Pickle, so I dropped it for now
How should second-order Zeeman shift be implemented in a way that's pickle-able?
In addition, states with a lot of hyperfine sublevels can't realistically be given second-order shifts level-by-level... Should a Breit-Rabi solver be built in to the package?