Measurements of the relative changes Delta lambda/lambda of the electron ca
pture rate is a direct experimental way to determine the changes Delta rho
(0) of electron density on the nucleus rho (0), which are necessary for the
determination of the Mossbauer isomer shift calibration constants. In this
paper we present our results obtained using various chemical compounds wit
h I-125 isotope. Fitting the results to the theoretical model, we find the
parameters, and using a genetic algorithm we solve the so-called "ill-posed
" problem. The calculated Delta lambda/lambda values compared with KIO3 are
(-2.9 +/- 0.3).10(-4) for Na3H2IO6, (-1.6 +/- 0.1).10(-4) for KIO4; (-1.4
+/- 0.6).10(-4) for CsI.