Fundamental Characteristics of Degenerate Four-Wave Mixing Spectroscopy for Combustion Diagnostics.

点击翻译按钮获取中文摘要

Buffer gas pressure dependence and temperature dependence of degenerate four-wave mixing (DFWM) spectroscopy have been investigated experimentally and model formulations ware proposed. Resonant DFWM signal intensity from NO shows significant decrease with increasing pressure of buffer gases (He, NィイD22ィエD2, COィイD22ィエD2, OィイD22ィエD2) for a constant pressure of NO. The small discrepancy between buffer gas species indicates that not only quenching but also other collision processes such as rotational and phase changing relaxation are responsible, unlike laser-induced fluorescence (LIF). These effects were incorporated in a theoretical model in terms of pressure dependent linewidth of resonant absorption, by which the pressure and input power dependence was reasonably reproduced. Temperature dependence of a specific rotational line strength at constant total pressure is accounted by considering the temperature dependent linewidth in addition to the term from thermal equilibrium state density.