SummaryFree radicals are generated in liquid solutions by harmonically modulated photolysis of suitable substrates. Harmonic analysis of the absorbance as functions of wavelength and modulation frequency yields the optical spectra and the decay kinetics of the transient species. The experimental technique and the analysis are described in detail. Results on t-butyl, 2-propyl and benzyl radicals generated by photolysis of the corresponding dialkyl resp. dibenzyl ketones are reported. They confirm previous spectral assignments and show that the termination reactions are diffusion controlled.
The fluorescence of 9-fluorenone has been measured in various solvents. At room temperature and for non-hydrogen bonding solvents an emission with 19.3 I v", , , 12 1.4 . lo3 cm-' is found, whereas the fluorescence for hydrogen bonding solvents is broad and strongly red shifted, 16.71 17.5 . lo3 cm-'. For these solvents also a strong temperature dependence of the emissicm characteristics is observed. The effects are attributed to hydrogen bonding of excited singlet fluorenone. Further, the phosphorescence of 9-fluorenone is detected for ethanol and EPA (diethyl ether/2-methyl-butane/ethanol (99.5%) 5 : 5: 2 ) solutions, locating the lowest triplet nrc* state at 17,600 cm-'.
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