Experimental confirmation of barrierless reactions between HeH^+ and deuterium atoms suggests a lower abundance of the first molecules at very high redshifts

Vol. 699
1. Letters

Experimental confirmation of barrierless reactions between HeH^+ and deuterium atoms suggests a lower abundance of the first molecules at very high redshifts

As a channel to the formation of H2 in the early Universe, (HeH^+) +D -> HD^+) + H is an essential reaction in primordial chemistry. Although less important than the analogous reaction involving H, it is more easily studied in the laboratory. Cross-section measurements at the temperatures relevant to the cosmologically important chemistry of this molecule are a major contribution to early Universe chemistry. These measurements are matched to theoretical calculations, which show an excellent agreement, and reveal a reaction rate that is up to a factor of 10 greater at low temperatures (10 K) than previously assumed.