REMARKS CONCERNING THE INTERPRETATION OF LONG-TERM OUTGASSING-RATE MEASUREMENTS WITH THE HELP OF THE RISE OF PRESSURE METHOD BY THE THEORY OF MALEV

Generally, the outgassing rate of any solid drops down smoothly with i ncreasing time, according to the existing theories on outgassing. This behaviour is caused by the reduction of the gas concentration in the bulk, or by the reduction of the gas coverage on the surface as a cons equence of the outgassing process. Some publications, however, report on constant outgassing rates, which were observed for a period of more than 1000 h. This paper proposes to explain these surprising results, with the help of the theory of Malev, by outgassing, which is control led by desorption at a constant surface coverage; this in turn is caus ed by replacing every desorbing particle immediately by another gas pa rticle, which diffuses from the bulk to the surface. In the case of th e validity of these hypotheses, the outgassing rate is very strongly d etermined by the density of adsorption sites on the surface and can be influenced by surface impurities, oxides etc.