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Sum Frequency Generation imaging has been developed to study adsorption and reaction on surfaces. The SFG process involves the overlap of a 1064 nm beam and a tunable IR beam (2000-4000 cm^-1). In the laboratory, a picosecond Nd:YAG Laser (PL2143A/20) was utilized to generate the fundamental wavelength at 1064 nm. The laser has a 20 ps pulse duration, a maximum repetition rate of 20 Hz. The fundamental 1064 nm beam from the laser pumps the Optical Parametric Generator/Amplifier (OPG/OPA) (Laservision) to generate the tunable IR and the 532 nm beam. The microscope was constructed using a reflection configuration. The two beams involved in the SFG process in the microscope set-up are the fixed 1064 nm beam and the frequency tunable IR beam (2000-4000 cm^-1). Both beams are set to p-polarization, no output polarizer is used. The 1064 nm beam comes in at an angle of 60º while the IR beam is at an angle of 70º. When the two beams overlap exactly at the same time and space, the mixing generates the sum frequency generated beam at a specific angle of 62º. The energies of the two beams applied on the surface are the following: a) 1064 nm beam with an energy density ranging from 50-100 mJ/cm² and b) tunable IR beam has an energy around 30-50 mJ/cm². Initially, the coherent SFG beam passes through a short pass filter to cut-off the reflected 1064 nm beam. Then, it passes through a telescope system made from Nikon lens to maintain the 1:1 object to image size onto the grating. A long pass filter was also placed after the telescope to cut-off any 532 nm signal generated. The grating has the ability to recombine the details of the sample image perpendicularly onto the 10 x Mitutoyo objective. After magnification, a tube lens is placed to collimate the beam until it reaches the charged-coupled device (CCD) in camera (Princeton Instruments) as the detector (with 1024 x 1024 pixel array).

Sum frequency generation imaging is used to monitor, in situ, the reaction of cyanide ions with gold surface. The gold cyanide reaction is used as a model corrosion reaction. Spatial and chemical variations across the surface are observed as a function of time. The initial period resulted in the formation of linearly bound cyanide to gold and with continuous exposure of gold film to cyanide solution led to the presence of higher-coordinated gold-cyanide complexes. These species were identified by their specific position in the SFG vibrational spectrum (2105 cm^-1, 2140 cm^-1, 2170 cm^-1, and 2225 cm^-1). The relative amount of these gold-cyanide species varied across the surface as resolved by the sum frequency generation microscopy.  The reaction of metallic gold to the oxidized Au(III) complex is characterized by the formation of specific Au-CN complexes.  Each complex, from 1-4 coordinated CN ligands, is used as an indication of the reaction progress.  The results show that the corrosion reaction is non-uniform and species specific. In addition Sum frequency generation imaging microscopy has been used to investigate a self-assembled monolayer of an alkanethiol (octadecanethiol, ODT) on a mild steel surface as a corrosion inhibitor. The images are used to analyze the orientation of the alkanethiol monolayer and the distribution of orientation angles as well as defects in the film. Spectra of the alkane thiols are obtained in the CH-stretching region where the amplitude ratio of the CH₃ sym/CH₃ antisym is used to deduce the tilt angle orientation of the terminal methyl group.  By considering that in each selected region of interest (ROI) the monolayer adopts a delta-function orientation, each ROI is then used to deduce the ensemble and therefore both the average and distribution width of the monolayer orientation.  The results show that, on average, ODT forms an ordered monolayer on mild steel when compared to the same monolayer on gold. However, the image analysis suggests that the distribution of tilt angles and conformational defects is greater for ODT on a mild steel surface compared to ODT/Au.            Finally sum frequency vibrational spectroscopy is utilized as an imaging technique to distinguish and compare the local response of carbon monoxide (CO) covered platinum (Pt) polycrystalline surface versus the average response of the investigated area. The Pt electrode was prepared using the standard method and was exposed to ~ 1 atm of CO(g). SFG images and vibrational spectra were obtained were the contrast is based on the intrinsic nature of each peak in the CO vibrational spectrum. The illustration of the images and the chemical maps of CO on platinum surface showed the distribution of the CO across the observed area. The results obtained by comparing the local and the average response confirmed the spatial distributions of the CO on platinum sample which are due to several reasons such as dipole-dipole coupling and surface coverage. This finding has a significant contribution toward recognizing that surfaces usually considered homogeneous may in fact be quite heterogeneous.