Detection of Ambient NO by Laser-Induced Photoacoustic Spectroscopy Using

摘要

Trace concentrations of NO are detected under ambient conditions by laser-inducedphotoacoustic spectroscopy. NO is excited via its A(2)sigma(+)-X(2)Pi (0,0) band with radiation near 226 nm, and the subsequent heat released is monitored by a microphone. Rotationally resolved photoacoustic spectra are recorded and fit using a multiparameter computer simulation based on a Boltzmann distribution. Transition probabilities and rotational energies are used as input parameters. The effect of buffer gas pressure, buffer gas, laser energy, and NO concentration on PA signal is investigated both experimentally and by model calculations. Units of detection of 1.2,2.8, and 4.9 ppm are obtained for NO in Ar, N2, and air, respectively. The ultimate sensitivity of this approach is greater with LODs projected in the low parts per billion by utilizing higher laser energies and an improved system design. The results are compared with previous studies using complementary laser-based spectroscopic techniques.