Аннотация:The modern Free-Electron-Lasers generate a highly intense polarized radiation which initiate asequence of ionization and decay events. Their probability depends on the polarization of eachstate as function of time. Its complete accounting is limited by the fact that a state can be formedin various ways. Here we present the equivalent of rate equations for population that completelyaccounts polarization of radiation and formulated in terms of the statistical tensors. To illustrateour approach we theoretically consider sequential photoionization of krypton by an intense extremeultraviolet femtosecond pulse for the photon energies below the 3d-shell excitation threshold. Thecalculations of the ion yields, photoelectron spectra and ionic polarization for various photon uenceare presented and role of polarization is discussed.