Tests of atomic charge-exchange cells for collinear laser spectroscopy

The performance characteristics of two charge-exchange cells (CECs) with horizontal and vertical cell configurations were determined by neutralizing a 10-keV rubidium ion beam in a potassium vapor. The neutralization efficiency and the fluorescence line shape of the 5s S-2(1/2) <-> 5p P-2(3/2) (D-2) transition in neutral Rb-85 were investigated as a function of the reservoir temperature used to control the potassium vapor density. The CECs exhibited similar neutralization performance and at neutralization efficiencies greater than 25-50% an asymmetric line shape of the rubidium D-2 fluorescent signal was observed. The asymmetry was attributed to inelastic channels in the charge-exchange process. The rubidium D2 fluorescence line shape was fitted with a multiple Voigt function, which quantitatively models the inelastic channels. In the present Rb+ + K charge-exchange process, the optimum neutralization efficiency to accurately determine the centroid of the Rb D-2 resonance line shape was obtained by fitting single Voigt functions to the resonance spectra obtained at neutralization efficiencies where inelastic processes were negligible. (C) 2012 Elsevier B.V. All rights reserved.