Compoundhyphen;negativehyphen;ion resonance states and thresholdhyphen;electron excitation spectra ofNhyphen;heterocyclic molecules: Pyridine, pyridazine, pyrimidine, pyrazine, andsymhyphen;triazine

摘要

The thresholdhyphen;electron excitation spectra of theNhyphen;heterocyclic molecules pyridine, pyridazine, pyrimidine, pyrazine, andsymhyphen;triazine have been studied with a newly constructed electron spectrometer. These are presented, discussed, and compared with photoabsorption and, whenever possible, with electron impact spectral data. Optically forbidden andnrarr; pgr;*transitions have been observed. Two compound negative ion resonance (CNIR) states (``shape'' resonances) have been detected below the first excited electronic states of allNhyphen;heterocyclic molecules studied, except symhyphen;triazine for which only one CNIR state has been observed. These CNIR states are discussed in terms of the effect of a perturbation introduced by the more electronegative nitrogen atom(s) in the benzene ring on the two lowest (degenerate) antibonding orbitals of benzene.