Theory of averaged low energy electron diffraction data

Averaged LEED spectra can be fitted with good accuracy by a curve of kinematic form. However, theoretical arguments show that a true kinematic average is impossible. The paradox is resolved by a new theory which shows that averages have a quasi-kinematic form with parameters different from those of the true kinematic theory. Some of the new parameters can be simply related to old ones, but others involve complicated corrections. Finally second order averaging schemes are proposed whereby more information can be extracted from experiments.