Extraordinary ray (e); Room temperature.
1) W. L. Bond, G. D. Boyd and H. L. Carter Jr.. Measurement of the refractive indices of several crystals , J. Appl. Phys. 36, 1674-1677 (1965)
2) Handbook of Optics, 3rd edition, Vol. 4. McGraw-Hill 2009* Ref. 2 provides Sellmeier equation based on the data from ref. 1
Strontium molybdate, SrMoO4