Evaporation/condensation coefficients as determined by the multiple Knudsen effusion cell method

We propose a new description of the Knudsen effusion cell flows in the case of two surface samples of different materials reacting by the intermediate of the gas phase. The behavior of each gaseous species on each surface are described by evaporation and condensation coefficients; for example, in the study the interaction between two surfaces, one of C and the other of Al2O3, the evaporation coefficient of Al is different for the Al2O3 surface and for the C surface. Guidelines for mass spectrometric experimental strategy are presented.