[en] The effective Hamiltonian formalism has been used in the development of a model for infrared multiple-photon absorption (IRMPA) process in symmetric top molecules. A computer program has been written and used for the calculation of the number of photons absorbed by Si₂F₆ as a function of the exciting laser frequency and for different laser fluences. The theoretical results are compared with the experimental ones and discussed in an attempt to explain the origin of the structures observed in the Si₂F₆ IRMPA spectra. (author)