He（2^3S1）,NE（^3P0,2）与NH3的传能动力学

The Energy Transfer Dynamics of He(2~3S_1) and Ne(~3P_(0,2)) with NH_3

在分子束条件下利用化学发光技术研究了亚稳态惰性气体原子He（23S1）和Ne（3P0，2）与NH3碰撞的解离激发反应．He（23S1）与NH3的反应中观察到NH（A－X，c－a，c－b），NH＋（B－X）和H*－Balmer发射．对NH（A－X，c－a）的谱图进行了拟合．分析NH（c－b）谱发现NH（c）倾向于生成具有f对称性的转动能级，NH3可能是经由一个NH2中间体分两步解离，这与121．6nm光解NH3时的倾向性正好相反．利用参比反应测得生成NH（A，c）的速度为k＝1．0×10－11cm3·s－1．He（23S1）与NH3生成的NH（A，v’＝1）的转动激发比v’＝0时要高，根据含角动量守恒的相空间理论，其生成过程可能具有较大的解离半碰撞参数．Ne（3P0，2）与NH3反应只有NH（A－X，c－a）发射，NH（A，c）的振转布居可由简单相空间理论三体解离模式解释．

Energy transfer reactions from He(23S1) and Ne(3P0,2) to NH3 have been studied by observing emission spectra from excited fragments at crossed molecular beams.Metastable rare gas atoms are generated by dc. discharge in the molecular beams. NH(A-X,c-a,c-b), NH+(B-X) and H*-Balmer emission systems were observed in the He(23S1)reaction, while only NH(A-X,c-a) was observed in the Ne(3P0,2) reaction. The absolute cross section of NH(A,c) from He(23S1) was determined to be σ=0.56A2 by using the reference-reaction method. The NH(c) has a large propensity to populate f rotational level in He(23S1)+NH3 reaction, and this is considered to come from a two-step disso ciation process. The propensity is opposite to that of NH3 photolysis at 121.6nm. The rotational excitation of NH(A,v=1) is somewhat higher than that of NH(A, v=0) and this may be the result of a large half-collision parameter according to the phase-space theory including angular momentum conservation. The ro-vibrational population of NH(A) and the rotational population of NH(c) can be intepreted with a simple phase-space theory of three-body dissociation in the reacton of Ne(3P0,2)+NH3.