The indices of refraction of potassium pentaborate, KB5O8.4H2O, have been measured over a range of wavelengths and the results fitted to a Sellmeier equation. No indication of an approaching absorption edge is found in transmission measurements from 0.56 to 0.20 µ.
© 1976 Optical Society of America
William R. Cook Jr. and L. M. Hubby Jr., "Indices of refraction of potassium pentaborate," J. Opt. Soc. Am. 66, 72-73 (1976)