  The state dependent quenching mechanism of metastable antiprotonic He atoms
by contaminants is suggested to explain existing experimental data. The effect
of antiproton transfer from the antiprotonic He to noble gas contaminants is
shown to play a significant role. Preliminary estimations have been done in the
framework of the coupled channels model. The obtained results support the idea
of strong dependence of quenching cross-sections on the antiprotonic states
quantum numbers and enable to explain qualitatively existing discrepancies
between experimental results, obtained for different contaminant densities. New
observable effects are predicted.
