A continuous flowing ethoxy CH3CH2O radical beam is produced in situ by pyrolysis of CH3CH2ONO at 223(+/-0.5)degreesC. By combining the HeI photoelectron spectrum with the improved density function theory (DFT) calculation, we have concluded that the CH3CH2O radical has C, symmetry and the ground state of the CH3CH2O+ cation is the (3)A " State which comes from removal of an electron of the SHOMO 10a ' orbital for the CH3CH2O radical. Both the photoelectron spectroscopy (PES) experiment and the DFT calculations not only provide another example of exchanging order of the ionic states for the species studied, but also the first example in which there has been almost the same vibrational structure on different ionic states caused by electron ionization on an orbital.