PT - JOURNAL ARTICLE AU - Novotný, Oldřich AU - Wilhelm, Patrick AU - Paul, Daniel AU - Kálosi, Ábel AU - Saurabh, Sunny AU - Becker, Arno AU - Blaum, Klaus AU - George, Sebastian AU - Göck, Jürgen AU - Grieser, Manfred AU - Grussie, Florian AU - von Hahn, Robert AU - Krantz, Claude AU - Kreckel, Holger AU - Meyer, Christian AU - Mishra, Preeti M. AU - Muell, Damian AU - Nuesslein, Felix AU - Orlov, Dmitry A. AU - Rimmler, Marius AU - Schmidt, Viviane C. AU - Shornikov, Andrey AU - Terekhov, Aleksandr S. AU - Vogel, Stephen AU - Zajfman, Daniel AU - Wolf, Andreas TI - Quantum-state–selective electron recombination studies suggest enhanced abundance of primordial HeH<sup>+</sup> AID - 10.1126/science.aax5921 DP - 2019 Aug 16 TA - Science PG - 676--679 VI - 365 IP - 6454 4099 - http://science.sciencemag.org/content/365/6454/676.short 4100 - http://science.sciencemag.org/content/365/6454/676.full SO - Science2019 Aug 16; 365 AB - Though only recently detected in space, the helium hydride ion (HeH+) is thought to be the first molecule ever to have formed in the early Universe. Novotný et al. report state-specific rate coefficients for the dissociative reaction of HeH+ with electrons, obtained using a cryogenic ion storage ring combined with a merged electron beam (see the Perspective by Bovino and Galli). They detect substantial rotational dependence and a decrease of the rates for the lowest states of HeH+, far below the values listed in astrochemistry databases and those previously applied in early-Universe models. These results suggest high abundance of this important primordial molecule at redshifts of first star and galaxy formation.Science, this issue p. 676; see also p. 639The epoch of first star formation in the early Universe was dominated by simple atomic and molecular species consisting mainly of two elements: hydrogen and helium. Gaining insight into this constitutive era requires a thorough understanding of molecular reactivity under primordial conditions. We used a cryogenic ion storage ring combined with a merged electron beam to measure state-specific rate coefficients of dissociative recombination, a process by which electrons destroy molecular ions. We found a pronounced decrease of the electron recombination rates for the lowest rotational states of the helium hydride ion (HeH+), compared with previous measurements at room temperature. The reduced destruction of cold HeH+ translates into an enhanced abundance of this primordial molecule at redshifts of first star and galaxy formation.