Schematic of the VENUS apparatus: (1) Molecules (H₂S and CO) and H atoms (dissociated hydrogen) are injected into the first chamber through the different injection pipes under a pressure of 10⁻⁴ mbar. After passing through the second chamber, with a pressure closer to that of the main chamber, the molecules enter the main chamber and are focused onto the gold-coated substrate. While injecting the molecules, the FT-RAIRS records the infrared spectrum of the molecules arriving at the surface of the substrate. This graphical representation of the molecules displays a codeposition of CO, H₂S, and H. (2) The FT-RAIRS is stopped and the main chamber is heated while the QMS placed in front of the substrate is on. In this way, all the molecules that sublimate can be recorded by the QMS.