A multi-molecular beam/infrared reflection absorption spectroscopy apparatus for probing mechanisms and kinetics of heterogeneously catalyzed reaction from ultrahigh vacuum to near-ambient pressure conditions.

The article focuses on the design, construction, and initial performance of a novel multi-chamber experimental apparatus developed to study mechanisms and kinetics of heterogeneously catalyzed reactions over well-defined model catalysts across a broad pressure range—from ultrahigh vacuum (UHV, 10⁻¹⁰ mbar) to near-ambient pressure (NAP, up to 1000 mbar). The setup comprises three interconnected vacuum chambers: a preparation chamber equipped with standard surface science tools for catalyst fabrication and characterization, a UHV reaction chamber featuring two effusive molecular beams, Fourier-transform infrared reflection absorption spectroscopy (FT-IRAS), and quadrupole mass spectrometry (QMS) for operando studies under isothermal conditions, and a compact NAP reaction chamber equipped with polarization-modulation IRAS (PM-IRAS), three independent gas dosers, and QMS for flow or batch mode operation at elevated pressures. The apparatus enables in situ transfer of samples without breaking vacuum, independent dosing of multiple reactants, and simultaneous monitoring of surface adsorbates and gas-phase products, thereby bridging the pressure gap between fundamental surface science and technologically relevant catalytic conditions. Performance tests, including CO adsorption on Pd(111) from UHV to 900 mbar and temperature-programmed desorption, demonstrate the system's capability for detailed mechanistic and kinetic investigations under controlled conditions.