Fluorescence detected linear dichroism. A new method for studies of molecular orientation in uniaxial systems

Abstract

A theoretical and experimental description of a new light spectroscopic method for determination of second rank order parameters is presented. The linear dichroism is obtained from the total fluorescent intensity, measured by using an integrating sphere. The method has been tested on a dichroic sample consisting of a stretched polymer film with an incorporated dye (2,2′-diethyl thiocarbocyanide iodide). The main advantages of using emitted light are the high sensitivity and selectivity. With the method described the molecular orientation of a fluorophore in a mixture of other absorbing chromophores may be studied. It is also suggested that the integrating sphere should be used in determinations of excitation spectra and for measurements of fluorescence detected circular dichroism.