Photothermal beam deflection

IR photothermal beam deflection spectroscopy (PBDS) and measurements of IR spectra of solids over the range 3950-450 cm l made with an interferometer coupled with a detector which senses the photothermal effect by the deflection of a laser beam are described. PBDS is a general technique and requires no sample preparation all that is needed is to hold the sample at the IR focus. The sample must have a flat spot about 2 mm in diameter accessible to the IR and laser beams. As no sample cells per se are... 

The technique employed is IR-FT photothermal beam deflection spectroscopy (PBDS). It is an off-shoot of photoacoustic spectroscopy (PAS) [1] and is based on the "mirage detection of the photothermal effect invented by Boccara et al. [2] and shown to result in a spectroscopic technique of remarkable versatility and utility. Some applications of "mirage spectroscopy," mainly in the visible, and theoretical treatments, have been described [3 6]. The method has now been developed for use in the IR. The spectrometer and techniques are described in detail elsewhere [7], but it will be useful to give a brief outline of the principles. 

Some recent developments in IR techniques have included IR photoacoustic and photothermal beam deflection spectroscopy. In photoacoustic spectroscopy the IR wave incident to the solid surface of the catalyst is absorbed by the sample. The radiation is converted to a... 

An alternative technique is the so-called Photothermal Beam Deflection Spectroscopy [PBDS], based on the so-called mirage effect first reported by Boccarra and coworkers [39, 40]. In this case, the periodic temperature rise caused by the absorption of the modulated IR radiation (i.e. the photothermal effect) is detected optically because it causes periodic deflections of a laser beam passing close to the surface of the solid sample. The PBDS technique has some advantages over the PAS technique, because of its lower Hmits of sample dimensions, but it has disadvantages because of the critical geometric setup. Like PAS, PBDS can have advantages with respect to traditional IR technique for the detection of surface... 

Basically, there are two categories of FTIR spectroscopies reflection and nonreflection techniques [38], The latter class comprises either acoustic detection or emission from the sample itself. The techniques recognized here are photoacoustic spectroscopy (PAS), emission spectroscopy (EMS), and photothermal beam deflection spectroscopy (PBDS). These techniques will not be considered further in this chapter. The reader is referred to the literature [39-42], For adhesion studies the reflection techniques (SRIRS) are more important. The major classes of sampling techniques in SRIRS are ... 

The other difficulty in the IR studies of carbons using halide pellets is the exposure of the carbon material to atmospheric gases and vapors that tend to vitriate the results. The development of elaborate techniques for obtaining carbonaceous films and preparation of charcoals by carbonization under vacuum conditions broadened the scope of applications of IR spectroscopy to the study of carbons and their surface groups. Furthermore, the sensitivity of IR measurements has been largely enhanced by using Fourier-Transform (FT), Photoacoustic (PAS), and Photothermal Beam Deflection (PDS) IR spectroscopy. 

Infrared Photothermal Beam Deflection Spectroscopy Infrared photothermal beam deflection spectroscopy (IR-PDS) is better than PAS because it does not have a microphone near the sample. It involves two light sources. One is an interferometer that produces modulated radiations to illuminate the sample, and the other is a laser source that is placed so that its beam grazes the surface of the carbon sample. The absorption of the incident-modulated radiation beam by the sample produces heat, causing thermal gradients that deflect the laser beam. The deflected laser beam is detected by the detector, and the signal reproduced is a measure of the photothermal effect induced on the sample surface. The resulting... 

Robbins, R. J., Laman, D. M., and Falvey, D. E., Substituent effects on the lifetimes and reactivities of arylnitrenium ions studied by laser flash photolysis and photothermal beam deflection, /. Am. 

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