He I Ultraviolet Photoelectron Spectroscopic Studies of ω-Thienyl α-Cyano Polyenic Carboxylic Ethyl Esters Compounds

He I ultraviolet photoelectron spectra of some ω-thienyl α-cyano polyenic carhoxylic ethyl esters compounds: (1)(2)(3)(4) have been given in this paper. The assognment of the spectra are also done using MNDO molecular orbital calculation for each studied molecules. It is pointed out that the linear reduction of HOMO ionization cnergy（I_p） which is mainly π antibonding character of ethylcnic group with the increment of ethylcnic group number is fortunately the base of homologous linear rule of this series compounds. And it is also shown that the -CN group participates in the conjugative π bond of whole molecular system and the —COOC₂H₅ group acts only as the substitution.