Infrared spectra recorded for experiment 4a during the isothermal (a) and TPD (b) phases, over the 400–4000 cm⁻¹ range. Top (a): spectra were recorded every five minutes for four hours. Bottom (b): spectra were recorded every two minutes during the heating from the isothermal temperature (40 K) to 300 K. At T = 150 K, the abrupt decrease in all characteristic H₂O bands is attributed to water desorption. For readability, only the first and last spectra are indicated in the legends.