Rapid-scanning Fourier-transform infrared spectroscopy with photothermal beam-deflection (mirage effect) detection at the solid–liquid interface

1986 ◽  
Vol 64 (9) ◽  
pp. 1086-1092 ◽  
Author(s):  
Richard A. Palmer ◽  
Matthew J. Smith
Keyword(s):  
Fourier Transform ◽  
Ambient Noise ◽  
Fourier Transform Infrared ◽  
Liquid Interface ◽  
Beam Deflection ◽  
Mirage Effect ◽  
Ir Studies ◽  
Infrared Spectrometer ◽  
Solid Liquid Interface ◽  
Solid Liquid

Photothermal beam-deflection (mirage effect) detection in the mid-infrared with a commercial scanning Fourier-transform infrared spectrometer has been used to characterize various solid–liquid interface and surface-bound species. The inherently unfavorable ambient noise level and relatively high Fourier (photothermal modulation) frequencies associated with commercial scanning instrumentation are compensated by the thermal and refractive properties of the liquid beam-deflection medium, which enhance the signal. Preliminary results described illustrate the potential of the technique for infrared (IR) studies of electrochemistry, catalysis, corrosion, and other surface modifications, as well as for polarized IR single-crystal spectra.

The Reverse Mirage Effect: Catching the Thermal Wave at the Solid/Liquid Interface

1987 ◽  
Vol 41 (7) ◽  
pp. 1106-1113 ◽  
Author(s):  
Matthew J. Smith ◽  
Richard A. Palmer
Keyword(s):  
Single Crystal Silicon ◽  
Liquid Interface ◽  
Beam Deflection ◽  
Probe Laser ◽  
Back Surface ◽  
Crystal Silicon ◽  
Mirage Effect ◽  
Beam Center ◽  
Solid Liquid Interface ◽  
Solid Liquid

Detection of species at the solid/liquid interface using infrared spectroscopy is severely limited by the opacity of most liquids to the infrared beam. In this work we use a variant of the photothermal beam deflection (“mirage effect”) method to avoid this problem. With this variant of the method (the “reverse mirage effect”), the IR beam passes through a transparent solid first, and then is absorbed by a liquid medium or by chromophoric species at the solid/liquid interface. The probe laser beam grazes the nonilluminated (back) surface of the solid and is deflected by the thermal gradient in the liquid. Results are presented that were obtained with the use of the reverse mirage technique with single-crystal silicon as the transparent solid and the use of pure acetonitrile as the absorbing sample and beam deflection medium. Studies of the position of the laser probe beam center with respect to the Si/CH3CN interface reveal interesting qualities about photothermal detection within the absorbing medium. The resulting spectra are analyzed in terms of the Rosencwaig-Gersho model.

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