ABSTRACT
The development of high power radiation sources and more sophisticated electronics, including sensitive microphones and digital lock-in amplifiers, have allowed for significant advances in photoacoustic spectroscopy (PAS). Successful applications of PAS in gases and condensed matter have made this a notable technique and it is now studied and employed by scientists and engineers in a variety of disciplines. Once excited, numerous pathways exist for the energy to dissipate, but a preponderance of the light energy is removed through a non-radiative pathway or through sample heating, which is the basis for all photothermal phenomena, including PAS. The future of PAS for sensing applications includes the continued development of laser sources with respect to broad continuous tunability and decreased system sizes and power requirements. Investigating liquids using the PA technique is attractive as it allows optical absorption measurements to be made for optically opaque samples.
