This paper presents a new fitting formula about the ionization energies of organic homologue: NlogIkp=a+bn, where N, Ip, and n are total atom numbers composing the homologue, ionization energy, and numbers of the repeat unit, respectively, and a, b are constants related to the energy level. After making linear regression analysis between NlogIp and n, all the correlation coefficients obtained from 150 groups of photoelectron spectral data of 46 homologous series are higher than 0.997, and among them are 1.000 in 131 groups, so the excellent rate is 100 percent.

Key words: HOMOLOG, IONIZATION ENERGY, PHOTOELECTRON SPECTROSCOPY, ELECTRONEGATIVITY