SENSITIVE MEASURING SCHEME IN COLLINEAR FAST-ION-BEAM LASER SPECTROSCOPY: THE OPTICAL PUMPING, STATE-SELECTIVE NEUTRALIZATION AND PARTICLE DETECTION SEQUENCE.

A method has been developed to increase the sensitivity of collinear laser spectroscopy on fast alkaline-earth ion beams considerably. The measuring scheme consists of three steps: efficient optical pumping of the ground-state ions to a low-lying metastable state, state-selective neutralization by passage through a vapour charge exchange cell, and separate counting of neutralized and unreacted particles. The state selectivity is due to the dependence of the cross sections on the energy defects involved in the charge exchange reactions. The technique is demonstrated on stable strontium beams, and quantitative results about the sensitivity are derived. Application to very weak beams of isotopes far from stability and further developments are discussed.