Linewidth Variations in ESR Spectra of o‐Dinitrobenzene Radicals

The importance of doubly excited configurations is demonstrated by their percent weights in the IAI excited states of pyrrole, 1, 4-dihydropyridine, and cis-butadiene, these being, respectively, 12%, 37%, and 46%. The corresponding IBI excited states have less than 1 % doubly excited configurations. We have found that the inclusion of doubly excited configurations is of no particular importance in the lower excited states of styrene, indole, benzofuran, but has moderate effects on 2and 4-pyridone. Strong effects were observed with various geometrical isomers of aminobutadiene and butadienone. There is still insufficient experimental information to determine if the inclusion of doubly excited configurations is absolutely necessary to rationalize the spectral features of certain types of molecules. Theoretically, it seems hard to justify the arbitrary exclusion of doubly excited configurat.ions. Since both the ground and excited states are affected, the use of the technique requires the adjustment of the parameters in order to produce agreement with experiment. Because of this it is not safe to claim any great theoretical foundation for a particular set of parameters or parameter method. The author wishes to thank R. Daudel, O. Chalvet, G. Bessis for their help and to the hospitality of the Republic of France. This investigation was supported by a Public Health Service Fellowship No. 1-F2-GM-30, 752-01 from the Institute of General Medical Sciences.