Thermal energy collisions between metastable Ne?(2p 53s,3 P 0, 2) and H2(X,1Σ g + )

A crossed beam experiment is used to investigate the Ne*(2p ⁵ 3s,³ P _{0, 2}) ? H₂(¹Σ _g ⁺ ) collision at thermal energy (67 meV). The H₂ beam is supersonic, the Ne* beam is thermal. Different collision processes have been analyzed separately by means of a double chopping technique combined with a time of flight measurement. Ions produced by Penning effect and chemi-ionization have been separated from scattered metastable atoms by an accelerating electric field small enough to preserve a reasonable angular resolution: δ?(ions)=±5.5°, δ?(Ne*)=±1°, which allows a determination of differential cross sections. The attenuation method, combined with an absolute measurement of the total H₂ flux, has been used to measure the total cross section: σ _t =940±220a ₀ ² . Differential cross sections have been obtained, in arbitrary but unique unit, for the following processes: (1) elastic collisions, for a mixture (1:3) of para- and ortho-hydrogen; (2) rotationally inelastic collisions:J=0→2; (3) Penning ionization resulting into H ₂ ⁺ ions; (4) chemiionization yielding NeH⁺ ions.