Spectral Absorption and Fluorescence of Dyes in the Molecular State

Abstract

As Prof. R. W. Wood has stated on p. 648 of his ” Physical Optics” (3rd ed.) that no liquid or solution has been found to exhibit the slightest trace of resonance radiation, it seems of interest to record that the effect has now been observed. It has been found possible to prepare suspensions of many dyes in solids and liquids, which possess an extraordinarily narrow absorption band associated with fluorescence of slightly longer wave-length. Three more or less general methods of preparation have been discovered, which possess the common feature that they cause the dye to pass from the dissociated state in true solution, through a transitory molecular state which exhibits a characteristic absorption and fluorescence, to the crystalline state. The effect is shown in a particularly striking manner by the dye 1: 1 diethyl--cyanine chloride, for which details of the three methods of obtaining the molecular absorption spectrum are given.