Synchrotron infrared photoacoustic spectroscopy

Abstract

The use of synchrotron radiation ͑SR͒ as a far-and mid-infrared source in the measurement of photoacoustic Fourier transform infrared spectra of solids is demonstrated for the first time in this work. Initial experiments were performed at beamline U10A at the National Synchrotron Light Source, Brookhaven National Laboratory. For synchrotron photoacoustic spectroscopy to be feasible, it must yield results superior to those obtained with a conventional thermal ͑Globar ® ͒ source; accordingly, SR and Globar ® photoacoustic spectra recorded under similar conditions were compared in detail. The intensities of SR far-infrared photoacoustic spectra were found to be consistently greater than the corresponding Globar ® spectra. At shorter wavelengths, SR always underfills the effective aperture ͑or, alternately, sample size͒; SR is a superior source in a spectral region that is a function of this aperture. The high wave number limit of this region exhibits a power-law dependence on aperture size. This investigation also showed that the entire mid-infrared photoacoustic spectrum is more intense using SR and apertures smaller than approximately 0.5 mm.

Far-infrared photoacoustic spectra of tetracene, pentacene, perylene and pyrene

“…Further improvements in far-infrared PA spectroscopy may be obtainable through the use of synchrotron radiation (SR) instead of conventional thermal infrared sources [12]. Potential bands at low wavenumbers, such as those observed for tetracene and perylene in the current work, could be adjudicated by means of SR PA spectra.…”

Application of infrared photoacoustic spectroscopy in catalysis

“…Some of them contain general content of the use and application of FT-IR/PAS [22][23][24][25][26][27][28][29][30][31], others are more specific and are devoted to real-time PA parallel detection of products from catalyst libraries [32], step-scan and depth profiling analysis [33][34][35][36][37][38][39][40], the effect of particle size on FT-IR/PAS spectra [41][42][43][44], the temperature effect on PA signal [45], sample emission effects [46], and synchrotron IR/PAS [47]. During a PA measurement the sample is enclosed in a small, tightly closed sample compartment called PA cell [48][49][50][51][52][53][54].…”