Atomically resolved studies of reactions at industrial settings - novel design of an ultra high pressure, high temperature scanning tunneling microscope system for probing catalytic conversions

In order to observe heterogeneous catalytic reactions that occur well above ambient pressure and temperature, a modified version of the Pan-style STM motor has been designed and constructed in-house. The new design features a much reduced size and a rigid coupling to the sample, and has been tested to show much higher resonant frequency than conventional Beetle-style STM designs, providing the ability to image faster and yielding lower susceptibility to noise. A small flow reactor cell ($\sim $10 mL) has been constructed to house the new STM, whose samples and tips are accessible through a bayonet-sealed access port by the use of a wobble stick and a transfer arm. The reactor cell can be placed inside an UHV system to allow cleaning and characterization of sample before and after experiments, as well as continuous monitoring by mass spectrometry or gas chromatography through a leak valve. The new system also allows \textit{in vacuo} sample and tip exchange without exposing the system to impurities in air. As such, the new ultrahigh pressure scanning tunneling microscope is designed to allow successive STM experiments performed with precise control of temperatures between 300 K and 600 K and pressures between $<$10$^{-9}$ torr and 30 bars.