  The pi- + 2H -> n + n, pi- + 3H -> n + n + n, pi- + 3He -> n + d and pi- +
3He -> p + n + n capture reactions from the lowest atomic orbitals are studied
under full inclusion of final state interactions. Our results are obtained with
the single-nucleon and two-nucleon transition operators derived at leading
order in chiral effective field theory. The initial and final three-nucleon
states are calculated with the chiral nucleon-nucleon SMS potential up to N4LO+
augmented by the consistently regularized chiral N2LO three-nucleon potential.
We found that absorption rates depend strongly on the nuclear pion absorption
operator used, and its two-body parts change the rates by a few orders of
magnitude. The final state interactions between nucleons generated by the
two-nucleon forces are also important, while the three-nucleon interaction
plays a visible role only in the pi- + 3He -> n + d reaction. Our absorption
rate for the pi- + 2H -> n + n process is in good agreement with the
experimental data from the hadronic ground-state broadening in pionic
deuterium. The capture rates on 3He are also generally consistent with the
spectroscopic data within error bars, though our central values are found to be
systematically below the data. We show that for the three-body breakup
processes the dominant contributions to the absorption rates arise from the
quasi-free scattering and final-state interaction kinematical configurations.
