Room-temperature absorption by PH₃–H₂ mixtures in the ν₂ and ν₄ bands of phosphine (PH₃) has been measured for low pressures. Fits of these spectra are made to determine the width of isolated lines and line mixing in a first-order Rosenkranz approximation. From the previous determinations, we deduce remarks on the lack of accuracy of predicting the collisional process. With the first-order Rosenkranz approximation, the collisional parameters are considered linear with pressure. In this work, we have considered spectra recorded for three doublets: A₁ and A₂ lines in the ν₂ and ν₄ bands of PH₃ diluted with higher H₂ pressure. We show that the line shifts are nonlinear with perturber pressures, which requires testing the fits of the recorded spectra with profiles developed in the secondorder approximation of the perturbation theory. Consequently, the first- and second-order mixing coefficients are determined and discussed. Throughout this study, we also show that the change in the intensity distribution is provided by the population exchange between low energy levels for the two components of doublets A₁ and A₂ lines and is described through the second-order mixing parameter. Thereby, we show the mixing effect on line width.

PH ₃ –H ₂混合物在 ν ₂和 ν ₄磷化氢 (PH ₃ )带中的室温吸收已经在低压下进行了测量。对这些光谱进行拟合以确定一阶 Rosenkranz 近似中孤立线和线混合的宽度。从之前的决定中，我们推断出对预测碰撞过程缺乏准确性的评论。使用一阶 Rosenkranz 近似，碰撞参数被认为与压力呈线性关系。在这项工作中，我们考虑了为三个双峰记录的光谱：PH ₃的 ν ₂和 ν ₄波段中的A ₁和 A ₂谱线用更高的 H ₂压力稀释。我们表明，线位移与扰动压力是非线性的，这需要使用在扰动理论的二阶近似中开发的轮廓来测试记录光谱的拟合。因此，一阶和二阶混合系数被确定和讨论。在整个研究中，我们还表明强度分布的变化是由双峰 A ₁和 A ₂线的两个分量的低能级之间的总体交换提供的，并通过二阶混合参数进行描述。因此，我们展示了对线宽的混合效果。