Phosphine (PH₃) is a highly reactive and toxic gas. Prior experimental investigations of PH₃ pyrolysis reactions have included only low-temperature measurements. This study reports the first shock-tube measurements of PH₃ pyrolysis using a new PH₃ laser absorption technique near 4.56 μm. Experiments were conducted in mixtures of 0.5% PH₃/Ar behind reflected shock waves at temperatures of 1460–2013 K and pressures of ∼1.3 and ∼0.5 atm. The PH₃ time histories displayed two-stage behavior similar to that previously observed for NH₃ decomposition, suggesting by analogy that the rate constant for PH₃ + M ⇄ PH₂ + H + M (R1) could be determined. A simple three-step mechanism was assembled for data analysis. In a detailed kinetic analysis of the first-stage PH₃ decomposition, values of k_1,0 were obtained and best described by (in cm³·mol^–1·s^–1) k_1,0 = 7.78 × 10¹⁷ exp(−80,400/RT), with units of cal, mol, K, s, and cm³. Agreement between the 1.3 and 0.5 atm data confirmed that the measured k_1,0 was in the low-pressure limit. Agreement of the experimental k_1,0 with ab initio estimates resolved the question of the main pathway of PH₃ decomposition: it proceeds as PH₃ ⇄ PH₂ + H instead of PH₃ ⇄ PH + H₂.

中文翻译：

---

利用PH3激光吸收对PH3 + M⇄PH2 + H + M（M = Ar）的速率常数进行冲击管研究。

磷化氢（PH ₃）是一种高反应性和剧毒气体。先前对PH ₃热解反应的实验研究仅包括低温测量。这项研究报告了使用新的PH ₃激光吸收技术（接近4.56μm）对PH ₃热解的首次冲击管测量。实验是在1460–2013 K温度和〜1.3和〜0.5 atm的压力下，在反射冲击波后面的0.5％PH ₃ / Ar混合物中进行的。PH _3的时间历史记录显示出类似于先前对NH ₃分解观察到的两阶段行为，通过类推表明，PH ₃ + M⇄PH ₂的速率常数+ H + M（R1）可以确定。组装了一个简单的三步机制进行数据分析。在第一阶段PH ₃分解的详细动力学分析中，获得了k _1,0的值，并用（cm ³ ·mol ^–1 ·s ^–1）k _1,0 = 7.78×10 ¹⁷ exp（ -80,400 / RT），单位为cal，mol，K，s和cm ³。1.3和0.5 atm数据之间的一致性证明，测得的k _1,0在低压极限内。实验值k _1,0与从头估计解决PH的主通路的问题₃分解：它前进如PH ₃ ⇄PH ₂ + H代替PH ₃ ⇄PH + H ₂。