Pulsed-laser photoacoustics "listens" to molecular and solvation volume changes
Quantum Northwest (Spokane, WA) has introduced an instrument for pulsed-laser photo acoustic studies on solutions. The absorption of pulsed energy of a dye laser (pumped by a Q-switched Nd:YAG or nitrogen laser) causes heat release and/or molecular and solvation volume changes in an absorbing solution. These changes produce an acoustic pressure wave that is detected by a fast piezoelectric transducer. Deconvolution of the transducer response provides information about amplitudes of change as well as rates, giving thermodynamic and kinetic information. Measurements at different temperatures can distinguish between heat released and molecular volume changes. For example, in aqueous solutions at 4°C, the thermal expansion coefficient of water is zero, so only volume changes will be measured.
Diode bars pump solid-state crystals to high powers