EXPERIMENTAL STUDIES OF THE CORE EXCITATION OF IMIDAZOLE, 4,5-DICYANOIMIDAZOLE, AND S-TRIAZINE

The C and 1s and N 1s core level spectra of solid imidazole (IM) and 4 ,5-dicyanoimidazole (DCIM) have been recorded with ultrasoft X-ray abs orption spectroscopy (USXAS) by using both total electron yield (EY) a nd fluorescence yield (FY) detection methods. IM, DCIM, and s-triazine (TZ) were studied in the gas phase by using inner-shell electron ener gy loss spectroscopy (ISEELS). USXAS and ISEELS show sensitivity to co re level shifts, especially for IM at the nitrogen edge, where the two main N 1s --> pi resonances are observed with a separation on the or der of the core level shifts. The N 1s --> pi separation changes from 2.4 eV in the gas phase to 1.4 eV in the solid. We feel this may be c aused by hydrogen bonding in the solid. Addition of cyano groups to IM resulted in a decreased splitting of the N 1s --> pi resonances, dem onstrating that USXAS and ISEELS are also sensitive to changes in ring substitution.