Experimental study of one-electron capture by ground and metastable Ar2+ions from Na at 1.5 keV

Abstract
The cross sections for one-electron capture by the ground-state Ar2+(3P) ions, sigma 21, and by the metastable Ar2+(1D) ions, sigma 21*, have been measured independently by an optical attenuation method (OAM). Both the cross-sections are of the order of 10-14 cm2 and sigma 21* is about 1.3 times as large as sigma 21. The metastable fraction in the primary-ion beam has been estimated at 0.29+or-0.16 from the OAM combined with the beam attenuation method. The OAM provides a useful means to determine one-electron capture cross sections for the ground and metastable ions, in particular when both the cross sections are nearly the same. The validity of the present method is discussed in detail.