Kinetics of changing in optical transmittance of palladium nanolayers during interaction with hydrogen

The kinetics of changing in optical transmittance of palladium (Pd) nanolayers (about 10 nm thick, deposited on object glass substrates by thermal evaporation in vacuum) in hydrogen flow (100% H$_2$) in the temperature range of 300–335 K are studied. It is shown that the rate of changing of palladium optical transmittance at hydrogen flow rises linearly with increasing the temperature due to sorption of hydrogen by Pd layer. The rate of changing in optical transmittance of Pd layer during sorption and desorption of hydrogen is established to rise by about one order with increasing the temperature from 300 to 335 K. The curves describing the changing in optical transmittance of palladium nanolayer during hydrogen desorption have two distinct sections: linear and nonlinear. The linear section of the curve weakly depends on temperature, while the nonlinear section sharply rises with increasing the temperature. Such the changing of the rate in optical transmittance can be associated with phase transition from $\beta$- to $\alpha$-phase during hydrogen desorption from palladium.