Kinetic study of high-pressure Ar–H2O mixtures excited by relativistic electrons

Dissociation of the H2O molecule by collisions with metastable argon (3P2) was shown a few years ago to lead to the excitation of the first vibrational levels of A 2Σ+ excited state of OH. The present work consists of a detailed kinetic study of an e-beam excited Ar–H2O mixture to evaluate the potential interest of that reaction scheme for laser applications. In this study, we have mainly shown that OH* (A 2Σ+) is populated by an Ar++H2O pathway too and we give an estimate for the OH* (A 2Σ+) and OH (X 2Π) formation branching ratios. We have also estimated that Ar*2+H2O is a minor OH* pathway. These results and measurements of main reaction rates permitted us to give a kinetic model where the predicted time dependence of population are in good agreement with the experimental result. The feasibility of a radical laser based on the collisional dissociation scheme of molecules is discussed.