ABSTRACT
This chapter focuses on the fundamentals as required for a phenomenological understanding of the respective techniques and some showcase applications, which underline the potential of these techniques. Photoacoustic (PA) spectroscopy and the whole family of optothermal techniques avoid these problems and can offer many additional features such as optical depth profiling and spatially resolved absorption analysis with microscopic resolution, depending on the specific spectroscopic modality. Gas phase analysis is likely to be the most common application of PA spectroscopy. The selectivity of PA spectroscopy is governed by the wavelength of the light employed to excite the PA signal. Liquid phase analysis is an application of PA spectroscopy where the specific benefit of PA spectroscopy over conventional, all-optical absorption measurements is particularly evident. The principle of PA spectroscopy is the detection of the fraction of light that is converted into heat. That means that photoacoustics is a competitive effect to fluorescence.
