  We consider three-body recombination into deep dimers in a mass-imbalanced
two-component atomic gas. We use an optical model where a phenomenological
imaginary potential is added to the lowest adiabatic hyper-spherical potential.
The consequent imaginary part of the energy eigenvalue corresponds to the decay
rate or recombination probability of the three-body system. The method is
formulated in details and the relevant qualitative features are discussed as
functions of scattering lengths and masses. We use zero-range model in analyses
of recent recombination data. The dominating scattering length is usually
related to the non-equal two-body systems. We account for temperature smearing
which tends to wipe out the higher-lying Efimov peaks. The range and the
strength of the imaginary potential determine positions and shapes of the
Efimov peaks as well as the absolute value of the recombination rate. The
Efimov scaling between recombination peaks is calculated and shown to depend on
both scattering lengths. Recombination is predicted to be largest for
heavy-heavy-light systems. Universal properties of the optical parameters are
indicated. We compare to available experiments and find in general very
satisfactory agreement.
