Collisional matter-phase damping in Bose-condensed gas
  Collisional damping of the excitations in a Bose-condensed gas is investigated over the wide range of energies and temperatures. Numerical results for the damping rate are presented and a number of asymptotic and interpolating expressions for it are derived. 
L. I. Plimak, M. J. Collett and D. F. Walls