State-selective electron capture by Ar2+(3P,1D,1S) ions in He, Ne and Kr

The composition of a primary Ar 2+ ion beam is analysed with respect to 3 P, 1D and 1 S states by aid of the translational attenuation method (TAM). The corresponding fractions are found to be 0.48, 0.37 and 0.15, respectively. Measurements with the analysed beam show that electron capture by slow Ar 2+ ions depend sensitively on the initial projectile state population. Whereas in the Ne target Ar 2+ ( 3 P) ions give the main contribution to the electron capture reaction, in the He target the metastable 1 D 2 state of Ar 2+ is more effective by a factor of about 19. Finally, in krypton the translational spectrum is dominated by reactions of Ar 2+ ( 1 S 0 ).