Determination of nonhyphen;Boltzmann vibrational distributions of N2(X,vlsquo;) in He/N2microwavehyphen;discharge afterglows

摘要

We have extended a technique for studying the vibrational distributions of groundhyphen;electronichyphen;state, molecular nitrogen in the afterglow of a microwave discharge through mixtures of helium and nitrogen. The technique is based upon adding metastable helium atoms to the afterglow. The Heast;(2thinsp;3S) excites the N2(X,v) to N+2(Bthinsp;2Sgr;+u) in a Penninghyphen;ionization reaction. Since Penning ionization is a Franckndash;Condon process, the vibrational distribution of the N+2(B) product is determined by that of the N2(X,v) from which it was produced. The measurements show that the groundhyphen;state nitrogen distribution is highly nonhyphen;Boltzmann, with vibrationally hotter distributions being produced with lower mole fractions of nitrogen in the discharge. We have also observed the production of N+2(Cthinsp;2Sgr;+u) from Heast; Penning ionization of molecular nitrogen. This process is energetically allowed only if the vibrational energy in the groundhyphen;electronichyphen;state nitrogen exceeds 3.8 eV or 15 vibrational quanta.