Knowledge Bank

An attempt has been made to fit the envelope of the ultraviolet absorption spectrum of a polynuclear aromatic hydrocarbon in solution by Gauss functions of the form: $$\epsilon_{\nu} = \epsilon_{\max},e - \left(\frac{\Delta \nu}{\theta}\right)^{2}$$ where $\Delta \nu =\nu -\nu o,\nu 0$ being the frequency of the band center, and $\theta =\Delta \nu$ where $ϵ=ϵmaxe$. Such analyses have been carried out for the spectra of the twelve isomeric monomethyl-1, 2-benzanthracenes in n-pentane solution both at room temperature and at $-100\circ C$ over the range from 2300 to 4000 {\AA}. To obtain a satisfactory fit with the experimental curve it is sometimes necessary to introduce component bands which are totally sub-merged below the absorption envelope. In most cases where such ``hidden bands'' have been postulated for the room temperature spectra, they have subsequently been resolved in the low-temperature spectra. This substantiates the belief that such bands have a real significance and are not mathematical artifacts. From such curve analysis it is inferred that five distinct electronic band systems occur in the spectrum of 1, 2-benzanthracene between 2300 and 4000 {\AA}.