IDENTIFICATION OF RADIATIVE EMISSIONS RESULTING FROM ELECTRON RECOMBINATION OF O2H+ AND N2OH+ IONS

A flowing afterglow technique has been developed for distinguishing between radiations emitted from electron-ion recombination and those from other sources such as ion-neutral and neutral-neutral reactions. The technique utilizes a ps which rapidly attaches electrons to create conditions where electron-ion recombination can or cannot occur. This has enabled experimental conditions to be established that maximize the photon emission rates without having to create a situation where only one reaction process contributes to the emission, which inherently results in substantially smaller signal levels. Such a technique allows emissions from optically weak transitions to be detected. The application of the technique is illustrated for the the dissociative electron-ion recombinations of O2H+ and N2OH+ over the wavelength range 200-400 nm. From this study, the relative contributions of the vibrational levels of the OH(A2SIGMA+) state to these spectra have been obtained, and in the case of N2OH+, the relative significance of the NH(A3PI(i)) channel to the OH(A2SIGMA+) channel has also been determined. The variation with attaching gas concentration of the intensity of a spectral feature due to recombination has also been shown to be very different from the variation observed in a feature due to other reactions.