Extracting infrared QCD coupling from meson spectrum

In the framework of the Bethe-Salpeter formalism used in previous papers to evaluate the quarkonium spectrum, here we reverse the point of view to extract an "experimental" running coupling alpha(exp)(s)(Q(2)) in the infrared (IR) region from the data. The values so obtained agree within the erros with the Shirkov-Solovtsov analytic coupling for 200 MeV < Q < 1.2 GeV, thus giving a very satisfactory unifying description of high and low energy phenomena. Below I GeV however alpha(exp)(s)(Q(2)) seems to vanish as Q -> 0. The paper is based on a work in progress in collaboration with D. V. Shirkov.