1. Basic Principles.- Photoacoustic Effect in Condensed Matter -- Historical Development.- Opto-Acoustic Spectroscopy -- A Tool for the Study of Optical Spectra of very Transparent Materials.- Thermodynamic Models of the Photoacoustic Effect.- Frequency Dependent Photoacoustic Spectroscopy of Condensed Matter.- Photoacoustic Spectroscopies.- Comparison Between Photoacoustic and Other Spectroscopies.- Generation of Acoustic Waves in Liquids by Pulsed Lasers.- Piezoelectric Detection in Photoacoustic Spectroscopy. Theory and Application.- Photothermal Radiometry.- 2. Spectroscopic Applications.- Applications of Resonant Photoacoustic Spectroscopy.- Photoacoustic Fourier Transform Spectroscopy for the Visible and the Near Infrared.- Photoacoustic Spectra of Biliverdin Dimethyl Ester.- Quantitative Photoacoustic Spectroscopy of Phenolred Potassium Salt in Polyvinalalcohol.- In Situ Photoacoustic Spectroscopy of Copper Electrodes in Solution.- 3. Photoacoustic Detection and Monitoring.- Optoacoustic Relaxation of Periodically Irradiated Solutions.- Photoacoustic Analysis of Chemical Reactions: H-D Exchange in the System H2S-D2S.- PA-Method Monitors Exhaust Gas Concentrations.- Application of PAS on the Local and Spectral Identification of Adsorbed Molecules.- 4. Thermal Applications.- Optical Absorption Coefficient and Thermal Properties of Liquids, Measured by Photoacoustic Spectroscopy.- The Photoacoustic Effect at Phase Transitions.- Photocalorimetric Investigations of Energy Conversion Processes Using Photoacoustic Detection.- Relative Efficiency of Flat Plate Solar Collectors by Transmission Photoacoustics; Importance of Plate Vibrations in Signal Generation.- 5. Photochemistry.- The Photocycles of Bacteriorhodopsin in Buffered Aqueous Suspension Studied at Low Temperatures by Means of Photoacoustic Spectroscopy.- Photochemistry of Adsorbed Thioindigo Dyes.- Photoisomerisation of DODCI Studied by Photoacoustic Spectroscopy.- 6. Nondestructive Testing.- Optoacoustic and Photothermal Imaging and Microscopy.- 7. Magnetic Resonance.- EPR of CuS C4·5H2O and Fe(III)-TPP Detected by the Photoacoustic Effect.- Acoustic Detection of Magnetic Resonance.- Applications of the Photoacoustic Effect to Ferromagnetic Resonance and Electron Paramagnetic Resonance.- 8. Instrumentation.- Instrumentation for Photoacoustic Spectroscopy and Calorimetry of Liquids and Solids.- Photoacoustic Cell for Low Temperature PAS.- Photoacoustic Cells for Measurements at Various Temperatures and Pressures -- Design and Characterisation.- Self-Supporting Carbon Glass Films: A PAS Reference Sample.- A Photoacoustic Demonstration Experiment: Cheap and Easy.