In order to study the phototropism exhibited by certain monoazo dyes more completely, a shutter and a sample illuminator were constructed for use with a Cary Recording Quartz Spectrophotometer. By use of this device the dye solutions can be exposed to a strong light source during the dark periods of the chopping shutter of the instrument. In this way solutions which show a very rapid phototropic change can be studied.
JOHN H. GOULD and WALLACE R. BRODE, "Shutter-Illumination Device for the Study of Phototropic Dyes," J. Opt. Soc. Am. 42, 380-382 (1952)