In studies of surface states at the SiO2&sngbnd;Si interface, an exponential variation of the electron capture cross section with band‐gap energy has recently been observed. In these bias regions, the dispersion parameter &sgr;uswas also observed to tend toward zero. In this paper, it is shown that the &sgr;usvalues inferred from the data reduction may be spurious results, influenced strongly by the energy dependence of the electron capture cross section.