SPECTRAL DATA OF SURFACE VISCOELASTIC MODULUS ACQUIRED VIA DIGITAL FOURIER TRANSFORMATION

The time domain behavior of dynamic surface tension was experimentally observed for submicellar aqueous solutions (2 × 10-3 and 4 × 10-3 mole m-3) of the surfactant dimethyldodecylphosphine oxide. The frequency domain behavior was calculated. by mapping one domain into the other with the Fourier transform operator. Two consecutive numerical processing runs were performed with different discretizations of the same input signal (0.1- and 3.0-sec time intervals between readings, respectively). By choosing an appropriate part of the output array from each run, satisfactorily accurate spectra of surface viscoelastic modulus were obtained. Values of parameters, determined from the reported spectra on the basis of the Lucassen theory, compare favorably with those given in the literature (obtained from equilibrium data). © 1979.