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RESEARCH PRODUCT

Depletion of the excited state population in negative ions using laser photodetachment in a gas-filled RF quadrupole ion guide

subject

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International audience; The depopulation of excited states in beams of negatively charged carbon and silicon ions was demonstrated using collisional detachment and laser photodetachment in a radio frequency quadrupole ion guide filled with helium. The high lying, loosely bound 2 D excited state in C − was completely depleted through collisional detachment alone, which was quantitatively determined within 6%. For Si − the combined signal from the population in the 2 P and 2 D excited states was only partly depleted through collisions in the cooler. The loosely bound 2 P state was likely to be completely depopulated and the more tightly bound 2 D state was partly depopulated through collisions. 98(2)% of the remaining 2 D population was removed by photodetachment in the cooler using less than 2 W laser power. The total reduction of the excited population in Si −, including collisional detachment and photodetachment, was estimated to be 99(1)%. Employing this novel technique to produce a pure ground state negative ion beam offers possibilities to enhance selectivity, as well as accuracy, in high precision experiments on atomic as well as molecular negative ions.