The quantum effects in the kinetics of 4He sorption by mesoporous materials
A.V. Dolbin, M.V. Khlistyuck, V.B. Esel’son, V.G. Gavrilko, N.A. Vinnikov, R.M. Basnukaeva, and V.V. Danchuk
B. Verkin Institute for Low Temperature Physics and Engineering National Academy of Sciences of Ukraine 47 Nauki Ave., Kharkiv, 61103, Ukraine
Received October 15, 2015
The sorption and the desorption of 4He by the mesoporous silicate MCM-41 material have been investigated in the temperature interval 1,5–290 K. It is shown that at T = 25–290 K the thermal activation mechanism is dominant in the kinetics of the sorption of 4He atoms by the MCM-41 sample. Its activation en-ergy was estimated to be Ea ~ 164,8 K. At T = 12–23 K the diffusion of the 4He atoms in the MCM-41 was practically independent of temperature, which typically occurs when the tunnel mechanism of diffusion dominates over the thermal — activation one. The mobility of the 4He atoms in the MCM-41 channels changed at T = 6–12 K which may be indicative of the formation on cooling (or decay on heating) of the monolayer and subsequent 4He layers at the inner surfaces of the channels. Below 6K the diffusion coefficients of 4He are only slightly dependent on temperature, which may be attributed to the behavior of the quantum 4He liquid in the MCM-41 channels covered with several layers of 4He atoms.
PACS: 68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation; PACS: 68.43.Mn Adsorption kinetics.