Associative ionization in collisions between metastable hydrogen atoms

Absolute total cross sections have been measured for the reaction H(2s) + H(2s) --> H2+ + e- in the collison energy range 0.004-0.65 eV. Single beam measurements yield a cross section of 2.1 x 10(-15) cm2 at an average collision energy of 4.1 meV. Relative measurements performed with merged beams indicate, together with the absolute measurements, an overall E-1 energy dependence.