UV Spectral Properties of Phenylalanine Powder.

A technique is described which makes it possible to measure the absorption spectrum of phenylalanine powder. Reflectance spectra are used to calculate the amount of light scattered from the samples; thus, the treatment of the data makes it unnecessary to normalize the absorbance to some value known from other work. Further, the unique scattering in the spectral region of an absorption band can be found. The fluorescence quantum yield of phenylalanine powder at 300K is calculated to be 1.0 +/- 0.1, a sizeable increase over the value of 0.04 found for aqueous phenylalanine solutions.