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.