Gas Phase Ultraviolet Photoelectron Spectroscopic Study of Some Oxygen Heterocycles

The helium I photoelectron spectra of some oxygen heterocycles in the gas phase are systematically re-investigated. HAM/3 molecular obital calculations on the each molecule of the studied series have been firstly carded out. The order of experimental vertical ionization potentials of molecule can be not only predicted, but the induced effect and through-space （or through-bond） interactions which come from the substitution of oxygen atom in the ring can be also interpreted by HAM/3 calculations.