A NEW METHOD FOR CONFORMATIONAL-ANALYSIS BY PHOTOELECTRON-SPECTROSCOPY WITH APPLICATION TO ALKYL-SUBSTITUTED STYRENES

A new method for molecular conformational analysis using photoelectron spectral data was developed and applied to alkyl-substituted styrenes as an example. The dihedral angle between the phenyl ring and the olefinic group plane, theta , in each molecule is evaluated by comparing the observed difference between the first and the third vertical ionization energies, DELTA E**1**. **3//i v, with the empirically estimated DELTA E**1**. **3//i//v vs. theta curve, the alkyl substituent effect being taken into account by the first order perturbation theory. The new method gives reasonable results consistent qualitatively with those given by other former methods.