Publication Date:
2016-02-27
Description:
Sorption and desorption of 4 He by a mesoporous silicate material MCM-41 was studied in the temperature range of 1.5–290 K. It was shown that for T = 25–290 K the thermal activation mechanism is dominant in the sorption kinetics of 4 He atoms by an MCM-41 sample. Its activation energy was estimated as E a ≈ 164.8 K. For T = 12–23 K, the diffusion of 4 He atoms in the MCM-41 was practically independent of temperature, which typically occurs when the tunnelling mechanism of diffusion dominates over the thermally activated one. A change in the mobility of 4 He atoms in MCM-41 channels was observed at T = 6–12 K, which may be indicative of the formation upon cooling (or decay upon heating) of a 4 He monolayer and subsequent multilayers on the inner surfaces of the channels. Below 6 K, the diffusion coefficients of 4 He are only weakly temperature dependent, which may be attributed to the behavior of quantum 4 He liquid in the MCM-41 channels covered with several layers of 4 He atoms.
Print ISSN:
1063-777X
Electronic ISSN:
1090-6517
Topics:
Physics
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