RESEARCH ON RECOMBINATION REACTIONS BETWEEN POSITIVE AND NEGATIVE IONS BY USING A CROSSED ION-BEAM METHOD

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A crossed ion-beam apparatus of positive and negative ions was constructed, and applied to the following neutralization reactions leading to rare gas halide excimers :Ar^+(^2P_<1/2,3/2>) + SF_6^-→ArF(B,C,D) + SF_5, (1)Kr^+(^2P_<1/2>) + C_6F_5Cl^- →KrCl(B,D) + C_6F_5, (2a)Kr^+(^2P_<3/2>) + C_6F_5Cl^- →KrCl(B,C) + C_6F_5. (2b)ArF(B-X,C-A) and KrCl(B-X,C-A,D-X) excimers are observed in reactions (1) and (2), respectively. No significant change in ArF((B-X,C-A) excimers was found, when the Ar^+(^2P_<1/2>) spin-orbit component was removed by the addition of N_2 to Ar. This suggests that the Ar^+(^2P_<1/2>)/SF_6^- does not provide ArF^* excimer or it gives the same excimer band. The relative formation rates of KrCl(B : C : D) in reaction (2a) were 0.05 : 0.00 : 0.95, while those in reaction (2b) were 0.71 : 0.29 : 0.00. The formation rate of KrCl(C) was small in both reactions at low operating pressures below 10^<-3> Torr. It was therefore concluded that the small formation rate of KrCl(C) is not due to its relatively long radiative lifetime, but due to its intrinsic feature.In order to obtain detailed information on the reaction dynamics of recombination reactions, theoretical ab initio calculations have been carried out for the He_2^+/C_6F_6^- reaction leading to low lying He_2^* states.In a preliminary experiment of this research project, we discovered a number of new emissions from rare gas heterodimers and heterotrimers.