Negative ion formation from energetic collisions of cesium with CO2, CS2, and COS

An experiment is described in which cesium atoms, with kinetic energies in the range 10–350 eV, collide with CO₂, CS₂, and COS. The measured products are negative ions from charge exchange (NICE). The parent anions, ${\mathrm{CO}}_2^{-}\mathrm{,\hspace{0.17em}}{\mathrm{CS}}_2^{-}$ , and COS⁻ are observed, as are other fragment ions. Intensity ratios for the various anions are measured as a function of cesium atom energy. The electron affinity of CO₂, determined from crude threshold measurements, lies in the range −2.1 to −1.1 eV, with a precision of about ±0.25 eV.