Collision energy dependence of the chemiluminescent reaction: Ba+N2O→BaO+N2

The chemiluminescence spectrum of the reaction Ba+N2O→BaO+N2 has been studied using a crossed beam apparatus as a function of the collision energy over the range 0.1–0.6 eV. The relative importance of its red wing increases as the collision energy is raised. Moreover, the cross section associated to chemiluminescence at a wavelength λ of the range 450–700 nm goes through a maximum as the collision energy is varied, the position of which depends significantly on the value of λ. The importance of this effect cast some doubt about works, where the energy dependence of the ‘‘total’’ chemiluminescence is measured using a detector which does not have a constant response over the wide range of the chemiluminescence. The analysis of the present results reveals that increasing the collision energy results in lowering the average vibrational excitation present in the emitting states A 1Σ+ and A′ 1Π of the product BaO.