Ulrike Willer
Clausthal University of Technology, Germany
Title: Quartz-enhanced photoacoustic spectroscopy with electrical co-excitation
Biography
Biography: Ulrike Willer
Abstract
Photoacoustic spectroscopy relies on the temporally modulated energy input into a gas via absorption and the subsequent transfer into a sound wave that is measured. Th is transfer of energy from vibrational into translational modes is highly dependent on collision partners and linked relaxation rates. For quartz-enhanced spectroscopy (QEPAS) a micro-tuning fork is used as a transducer instead of a conventional microphone and the modulation of the excitation laser is done at the resonant frequency of the tuning fork for signal enhancement. However, it is not only possible to drive the tuning fork into oscillation by the photoacoustically generated acoustic wave but also by applying a modulated voltage. With these two diff erent driving forces, either applied simultaneously or subsequently, it is possible to gain more insight of the properties of the gas and the relaxation dynamics. Th is is especially valuable if the background gas and with it the collision partners, density, velocity of sound and relaxation rates change and a variation in signal cannot unambiguously attributed to a variation in concentration. It will be discussed how the photoacoustic interaction can be used to promote an originally electrically induced tuning fork oscillation or to fasten its fading, which enables the measurement of times rather than intensities.