Consider what the correct chi2 value is supposed to be.

[andyfaff]

In eqn 2 of https://www.sciencedirect.com/science/article/pii/S0925346720307862 a very different chi2 value is used to do least squares analysis of the ellipsometry data. Currently refellips works out traditional chi2 values for the psi and delta components and adds them together.

• what does wvase32 do, what does completease do?

[andyfaff]

On page 21 of http://terry.engin.umich.edu/wp-content/uploads/sites/385/2018/04/jellison.pdf they use a normal chi2 on the rho value. $\rho = tan(\psi) * exp(i\delta)$, fitting the imaginary and real parts simultaneously.

[andyfaff]

WVASE appears to what we use: https://www.seas.upenn.edu/~nanosop/documents/Session1A_UPenn_WVASE_Feb_2014.pdf, see slide 76

[andyfaff]

CompleteEASE is on pg 3-45 (eqn 2.2) of https://physlab.lums.edu.pk/images/f/f4/Ellipsometry_manual.pdf

@igresh, @haydenrob, should we update this?