Sample mounting and transfer mechanism for in situ IR-visible sum frequency generation vibrational spectroscopy in high-pressure ultrahigh vacuum system

Abstract

We developed a sample mounting and transfer mechanism for studying heterogeneous catalytic reactions in a high-pressure ultrahigh vacuum system. The system is optimized for the use of sum frequency generation vibrational spectroscopy to probe surface species in situ during the reactions. The system allows wide-ranging working conditions: a pressure range between 4×10−10 and 760 Torr and a temperature range between 200 and 1200 K. Rigid and reproducible sample positioning as well as precise temperature control can be achieved by compact designs of a sample holder and a sample mount incorporating ultrahigh vacuum compatible plugs. The performance of the system is demonstrated here by monitoring surface intermediates over time during cyclohexene catalytic reactions using a Pt(111) single crystal and sum frequency generation vibrational spectroscopy.

Hydrogenation and dehydrogenation of cyclohexene on Pt(100): A sum frequency generation vibrational spectroscopic and kinetic study

“…This was necessary because gas molecules in the HP cell absorb some of the incoming radiation. Detailed descriptions on the HP/UHV system and SFG measurement can be found elsewhere [18,19].…”

Surface science under reaction conditions: CO oxidation on Pt and Pd model catalysts

“…In addition, the intensities of both types of polarized photons are dependent on gas-phase absorption, which means that the reflection of s-polarized light exclusively yields gas-phase information, while the difference in reflection between p-and s-polarized light contains surfacespecific information. Several systems have been realized that attach a high-pressure cell for PM IRRAS 28 or for SFG spectroscopy 29,30 to a UHV chamber. Polarized light is also used in ellipsometry and related techniques, such as ellipso-microscopy for surface imaging (EMSI) [31][32][33] and reflection anisotropy microscopy (RAM).…”

Sum Frequency Generation Vibrational Spectroscopy and Kinetic Study of 2-Methylfuran and 2,5-Dimethylfuran Hydrogenation over 7 nm Platinum Cubic Nanoparticles

“…The signal-to-noise ratio was further enhanced by a gated integrator, while the IR beam was scanned through the spectral region of interest. Additional information about the SFGVS system used in this study can be found elsewhere. − …”