The width at half-maximum of the band transmitted by a Christiansen filter has been measured for ten wave-lengths, and for glass grains of six sizes in ethyl salicylate. With a cell 7.5 mm thick, the grain size affording the narrowest bands was found to be about 0.7 mm, depending somewhat upon wave-length. Bands have been observed in the violet, having a width at half-maximum as narrow as 8 to 1OA, the transmission at peak being about 40 percent.
H. S. DENMARAK and WILLOUGHBY M. CADY, "Optimum Grain Size in the Christiansen Filter," J. Opt. Soc. Am. 25, 330-331 (1935)