Invariants of reflectometry curves and the structural features of thin films

It is shown that the integral of the autocorrelation function of freestanding layered films determines the square of the mean electron density in the film cross section. Data-processing techniques are proposed to deal with the results of reflectometry measurements for films on substrates. Comparison of the autocorrelation functions calculated on the basis of the experimental curve and the model provides an opportunity to evaluate the sample quality.