Experimental Results for H 2 Formation from H − and H and Implications for First Star Formation

Abstract

Early Rising Hydrogen Formation of molecular hydrogen through electron-expelling collisions of H atoms and H − anions is regarded as a key step in the cooling process that led to assembly of the first stars in the early universe. Kreckel et al. (p. 69 ; see the Perspective by Bromm ) performed highly precise laboratory measurements of the rate of this reaction at a range of different energies. The study required construction of a dedicated apparatus to carefully tune the relative velocity of merged atom and ion beams. The data validated prior theoretically calculated reaction cross sections, which were then extended for use in cosmological models.