Compact ultrahigh vacuum/high-pressure system for broadband infrared sum frequency generation vibrational spectroscopy studies

We have designed a compact ultrahigh vacuum/high-pressure system for in situ broadband infrared (IR) sum frequency generation vibrational spectroscopy (SFG-VS) studies. In this system, we have achieved a significant reduction in the distance between the sample and the optical window (<5 mm), which in turn considerably reduces the IR absorption from the gas phase under high pressure conditions. Moreover, with this new system, the IR transmission under high pressure conditions can be measured in situ for calibrating the SFG spectra. Therefore, this modified technique can allow us to study the vibrational spectra of adsorbates on single crystals or polycrystalline foils under high pressure. The preliminary results from SFG measurements of a model CH3OH/TiO2(110) system under both ultrahigh vacuum and high pressure conditions are reported here. These results suggest that this newly developed system is potentially a powerful tool for investigating adsorbate structures and surface reactions under both ultrahigh vacuum and real conditions. (C) 2016 AIP Publishing LLC.