Cross section of the formation of mesic molecular complex (MMC) in the reactions
(t μ)F +(D2)νiKi→ [(dt μ) JvS dee] νfKf is calculated at low energies (E < 100 K). We assume the Breit-Wigner energy dependence of the cross section. In calculating the entrance widths the electron screening and various orbital moments of the incident tμ-atom were taken into account. Owing to anharmonic corrections to a purely harmonic approximation the reduced entrance width remains nonzero at E → 0. As the result the conventional 1/v law for energy dependence of the MMC formation cross section is restored. The entrance width for the transition
(νi = 0, Ki = 0) → (νf=2, Kf=1) proves to be the most important. The wave functions of D2 and MMC were calculated in the Morse potential which proves to give the level positions with a high precision and includes anharmonic corrections to full extent. Accounting for the anharmonism modifies considerably both the energy dependence and the value of the MMC formation cross section. Comparing calculated rates with the experimental data one can estimate the positions of the resonance levels.