CARACTERIZACIÓN DE LA ESPECTROSCOPÍA FOTOACÚSTICA PULSADA DEL NO2 EN AIRE

The photoacoustic technique, based on an Nd:YAG pulsed laser at 532 nm, was used to investigate a binary gas mixture of NO2 and air contained in a cylindrical glass cell. In order to improve the method, some characteristic parameters, cell quality factor and resonance frequency were analyzed. As the buffer gas pressure increases, the former rises and the latter lowers. At total low pressure (around 1 Torr), the excited molecules decay, through visible fluorescence emission, at a rate similar to the heating process. With a fast photodiode the record and analysis of fluorescence allowed deducing electro-vibrational energy to kinetic relaxation times. In order to verify the systems linearity, the photoacoustic signal behavior of NO2 (0.2 Torr) in air at atmospheric pressure was studied as a function of laser fluence in the 0.003 to 1.8 J/cm2 range.