A comparison of molecular orbital methods for the analysis of the He(I) photoelectron spectra of n-alkenes

The two highest vertical ionization potentials are calculated by the Fenske-Hall, MINDO/1, and MINDO/3 molecular orbital methods for an extensive series of n-alkenes. It is found that the Fenske-Hall method gives a better correlation with the corresponding experimental photoelectron spectral data and is the most useful for the interpretation and understanding of these results. When MINDO/3 was used for calculations by the ΔSCF method, it was not possible to obtain satisfactory agreement with the photoelectron spectroscopic measurements. Finally, the relevant findings of other calculational procedures such as ab initio and SPINDO are given.