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Science. 2019 Aug 16;365(6454):676-679. doi: 10.1126/science.aax5921. Epub 2019 Jul 18.

Quantum-state-selective electron recombination studies suggest enhanced abundance of primordial HeH.

Author information

1
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. oldrich.novotny@mpi-hd.mpg.de.
2
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
3
Faculty of Mathematics and Physics, Charles University, 18000 Praha, Czech Republic.
4
Institut für Physik, Universität Greifswald, 17487 Greifswald, Germany.
5
Rzhanov Institute of Semiconductor Physics, Novosibirsk 630090, Russia.
6
Weizmann Institute of Science, Rehovot 76100, Israel.

Abstract

The 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.

PMID:
31320559
DOI:
10.1126/science.aax5921

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