Kinetics and mechanism of the reactions of PH3 with O(3P) and N(4S) atoms

Abstract

The reactions of ground-state oxygen and nitrogen atoms with phosphine have been studied using a discharge-flow system with detection of both free-radical and molecular species by molecular-beam sampling mass spectrometry. By observing the decay of PH₃ in an excess of O, the rate constant for the reaction O + PH₃ [graphic omitted] products (1) was determined to be k₁=(4.6 ± 0.8)× 10^–11 cm³ molecule^–1 s^–1. The products are principally H₂PO and H with <10% of the reaction proceeding to PH₂ and OH. Observation of the molecular species H₃PO is reported for the first time. HPO and PO were also detected and a new mechanism for the reaction of oxygen atoms with phosphine is suggested. The reaction N + PH₃ [graphic omitted] products (2) was observed to be very slow with an upper limit for the rate constant of k₂⩽ 4.0 × 10^–14 cm³ molecule^–1 s^–1.