Ultraviolet Spectroscopy: Aromaticity of Carbonaceous Materials; Absorption Errors
SourceElectronic spectra of carbonaceous materials that are devoid of specific absorption bands may be used to determine limits of polynuclear condensed aromaticities in carbonaceous materials. Band intensity and absorption area methods are described. The maximum polynuclear aromaticities of coal and of coal asphaltene are found to be considerably lower than expected and necessitate the presence of large concentrations of saturated structures. Sources of error in absorption spectra of aromatics are discussed. Several methods are described for the detection and quantitative measurement of fluorescence errors in absorption spectra of a solution, at a specific concentration, and of thin films. The path-length-extension method permits quantitative determination of fluorescence nonlinearity through measurements on a single sample.