A more complete interpretation of optoacoustic data taken with fixed‐frequency lasers

摘要

The response of the cylindrical optoacoustic cell when filled with an absorbing gas and irradiated by a laser beam passing along its axis has been studied theoretically and experimentally as a function of the gas pressure and composition. The pressure on the cell microphone has been calculated by solving numerically, for the experimental parameters of interest, the general heat‐diffusion equation with a forcing function which is shown to depend upon both space and time for the realistic case of 50 modulation of the laser beam. It is further shown that if the experimental optoacoustic signal at a given pressure is divided by the signal calculated for that pressure, the ratio is expected to be a constant. The results of a series of experiments using a CO laser to irradiate mixtures of nitric oxide (the absorbing gas) and nitrogen are presented and are shown to confirm the theoretical predictions.