The effects of temperature and pressure on laser-induced fluorescence (LIF) of OH are numerically studied under the excitation of A–X (1,0) transition at high pressures. A detailed theoretical analysis is carried out to reveal the physical processes of LIF. It is shown that high pressure LIF measurements get greatly complicated by the variations of pressure- and temperature-dependent parameters, such as Boltzmann fraction, absorption lineshape broadening, central-frequency shifting, and collisional quenching. Operations at high pressures require a careful choice of an excitation line, and the Q 1 (8) line in the A–X (1,0) band of OH is selected due to its minimum temperature dependence through the calculation of Boltzmann fraction. The absorption spectra of OH become much broader as pressure increases, leading to a smaller overlap integral and thus smaller excitation efficiency. The central-frequency shifting cannot be omitted at high pressures, and should be ta...

中文翻译：

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温度和压力对高压下OH激光诱导的荧光激发A–X（1,0）跃迁的影响

在高压下，在A–X（1,0）跃迁的激发下，数值研究了温度和压力对OH的激光诱导荧光（LIF）的影响。进行了详细的理论分析以揭示LIF的物理过程。结果表明，由于压力和温度相关参数（例如玻耳兹曼分数，吸收线形加宽，中心频率偏移和碰撞猝灭）的变化，使得高压LIF测量变得非常复杂。在高压下运行需要仔细选择激励线，并且通过计算玻耳兹曼分数，由于其对温度的依赖性最小，因此选择了OH的A–X（1,0）带中的Q 1（8）线。OH的吸收光谱随着压力的增加而变得更宽，导致较小的重叠积分，从而减小励磁效率。中心频率偏移在高压下不能忽略，应加以注意。