Release of large polycyclic aromatic hydrocarbons and fullerenes by cosmic rays from interstellar dust

Swift heavy ion irradiations of interstellar carbonaceous dust analogue

¹ Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris Sud, Université Paris-Saclay, 91405 Orsay, France
e-mail: thomas.pino@u-psud.fr
² Institut de Physique Nucléaire d’Orsay (IPNO), IN2P3-CNRS, Univ. Paris Sud, Université Paris-Saclay, 91405 Orsay, France
³ Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), CNRS/IN2P3, Univ. Paris Sud, Université Paris-Saclay, 91405 Orsay, France
⁴ Fakultät für Physik, Universität Duisburg-Essen, Duisburg, Germany
⁵ GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany
⁶ Technische Universität Darmstadt, 64287 Darmstadt, Germany
⁷ Institut d’Astrophysique Spatiale (IAS), CNRS, Univ. Paris Sud, Université Paris-Saclay, 91405 Orsay, France
e-mail: emmanuel.dartois@u-psud.fr

Received: 13 December 2018
Accepted: 3 February 2019

Abstract

Context. Top-down chemistry is believed to be responsible for the formation of the large molecular compounds such as the polycyclic aromatic hydrocarbon-like molecules and the fullerenes observed in the interstellar medium. The release of these large molecules from the parent grains remains an important issue to be investigated.

Aims. Cosmic rays irradiate the dust grains during their journey in the interstellar medium. In this study we probe to what extent electronic sputtering and/or desorption processes induced by high-energy ion projectiles contribute to the creation of the large molecular component in space.

Methods. Carbonaceous dust analogues were produced in an ethylene flame. The resulting soot nanoparticles generated under well-defined conditions were irradiated by swift heavy ions, and mass spectra of the ionic and neutral molecular fragments emitted shortly after the impact were monitored.

Results. Large molecular fragments were detected, including neutral and ionic polycyclic aromatic hydrocarbons containing up to several tens of carbon atoms, as well as ionic fullerenes. Although the absolute efficiencies were not obtained, these experiments provide a proof of principle of a top-down scenario involving interaction processes of interstellar dust with high-energy projectiles yielding large molecular compounds observed in space.