ELECTRONIC ABSORPTION SPECTROMETRY OF RADIATION-PRODUCED RADICAL CATIONS - SPECTRAL DECONVOLUTION BY BLEACHING AND CONDITIONS FOR SPECTRAL PURITY

Electronic absorption spectra of radiation-produced radical cations in solid matrices at cryogenic temperatures are superimposed on matrix absorption (i.e. absorption resulting from irradiation of the matrix) and spectral deconvolution is required if pure spectra are to be obtained. This may be accomplished by difference spectrometry after selective removal of the radical cations studied by illumination (bleaching). The conditions for spectral purity are that no other species absorbing in the spectral region of interest disappear during the bleaching process and that no species absorbing in this region are formed by the bleaching process. The purity of the spectrum of heptane radical cations in 1,1,1-trichlorotrifluoroethane matrices is investigated as an example. It is concluded that different spectroscopic techniques may have to be utilised in order to decide on the spectral purity of the electronic absorption bands obtained by the deconvolution method described. © 1990.