The absorption spectra of some aromatic compounds

Summary

The absorption spectra of some quinones and hydroquinones in the vapour state have been studied over a wide spectral region, from 7000 to 2200 Å, with a high dispersion spectrograph. Many of them show a vibrational structure, and some of them also a rotational fine structure. The bands for the simplest of the molecules, namely benzoquinone and hydroquinone, have been analysed, and the characteristic vibrational frequencies of the normal and excited molecules have been determined. For the other molecules the vibrational frequencies for the excited state only could be so obtained.

The substances have been studied also in solution. The rotational and vibrational structures observed with the vapours are all quenched, and the maxima of absorption are considerably shifted towards the red end of the spectrum. In the solid state, in which also two of the substances were studied, there is a further shift of the absorption-maxima in the same direction.