活性氮反应产生激发态卤化氮实验研究

Electronically Excited NX(b)(X=F,Cl,Br) Formation by Active Nitrogen Reaction

报道了利用氮气放电产生的活性氮有效制备激发态卤氮自由基NX(b)(X=F,Cl,Br)的方法.在流动余辉装置上,将含溴有机物CH2Br2、CHBr3、C2H5Br、C4H9Br加入到活性氮中,在550～750nm观察到了较强的NBr(b→X)跃迁发射光谱.机理分析表明,活性氮中的基态氮原子N(4S)与含溴分子反应首先产生基态的NBr,由于亚稳态分子N2(A3Σ+u)的能量转移作用,基态NBr被激发到NBr(b).当含氯有机物CCl4、SOCl2加入到活性氮中时,观察到了NCl(b→X)的发射光谱,而当CHCl3、CH2Cl2加入到活性氮中时,却没有观察到NCl(b)态的辐射跃迁.当SF6与氮气混合放电时,观察到了NF(b)态的跃迁发射谱.分析表明,基态的NCl和NF自由基分别是由N(4S)+CCl3(SOCl2)→NCl(X)+CCl2(SOCl)和N(4S)+SF5→NF(X)+SF4通道产生的,再通过N2(A)能量转移到激发态.

A new method for producing electronically excited nitrogen monohalides NX （b） （X = F, Cl, Br） is reported. The strong emission spectra of NBr（b ^1∑^＋→＋X^3∑^-） are observed when alkyl bromides （CHBr3, CH2Br2, C2H5Br, and C4H9Br） are added to a stream of active nitrogen, generated by a hollow-cathode discharge of N2, in a flowing afterglow system. Some tentative experiments show that the electronically excited NBr（b） is formed by means of metastable N2 （ A^3∑u^＋ ） Electronic-to-Electronic energy transfer to NBr（ X）, which is from the reaction of N（4S） with alkyl bromides. The emission spectra of NCI（b^1∑^＋ →X^3∑^- ） are obtained when CCl4 or SOCl2 is admitted into a flow of active nitrogen, but neither CHCl3 nor CH2Cl2 addition results in such an emission. It has been proposed that the origin of the excited NCl （b） is an energy transfer from N2 （A） to NCl （X）, generated by the reaction of N（^4S） with CCl3 （or SOCl2）. Similar experiments are also carried out with SF6 as reagent of active nitrogen, or as mixture with N2 in the discharge. By recording fluorescence it was found that excited NF（b） is produced only under discharge through NE/SF6 mixture. The NF （b） state presumably arises from the energy transfer from N2 （A） to NF（ X）, and the latter is generated from the abstraction of fluorine by N（^4S） from SF5.