Continuous cryotrapping of hydrogen by argon in the temperature range between 4.2 and 15°K

Abstract

Hydrogen in the under-saturated condition can condense on cold surfaces if it is mixed with argon. The mixed condensation of argon and hydrogen for condensation surface temperatures in the region between 4.2 and 15°K was investigated. The results of the experiments showed that the trapping ratio, ie the number of argon atoms required to bind one hydrogen atom, rises exponentially with the temperature. In slow heating of the condensation surface, two maxima are observed in the hydrogen partial pressure curve. This behaviour suggests that binding of the hydrogen in the argon condensate takes place with two different binding energies. The binding energy of one of the two conditions is determined by measuring the hydrogen vapour pressure curve via the mixed condensate. It is approximately 700 cal/mol. This is greater than the evaporation heat of the pure hydrogen but less than the adsorption energy of hydrogen on metal surfaces.