  The electron-electron relaxation in impure two-dimensional superconductors is
studied. All channels of the electron-electron interaction classified in the
Nambu representation are taken into account. It is shown that the recombination
relaxation rate originates from quasipartical processes associated with
fluctuations of the electron density and the phase of the order parameter. At
low temperatures the recombination relaxation rate has a double exponential
temperature dependence. The scattering relaxation rate at low temperatures has
a power law temperature dependence due to contributions from gapless collective
excitations, the phase modes. Two-layer superconductor-normal metal system is
also considered. It is shown that the recombination relaxation rate in the
superconducting layer has a single exponential factor at low temperatures in
comparison with a one layer superconducting system. This increase in the
recombination relaxation rate originates from the inter-layer Coulomb
interaction and may be used in constructing of superconducting radiation
detectors.
