X-ray photochemistry of carbon hydride molecular ionsElectronic supplementary information (ESI) available. See DOI: 10.1039/c7cp08026c

• Main Authors: Puglisi, Alessandra, Miteva, Tsveta, Kennedy, Eugene T, Mosnier, Jean-Paul, Bizau, Jean-Marc, Cubaynes, Denis, Sisourat, Nicolas, Carniato, Stéphane
• Format: Article
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp08026c

Hydride molecular ions are key ingredients of the interstellar chemistry since they are precursors of more complex molecules. In regions located near a soft X-ray source these ions may resonantly absorb an X-ray photon which triggers a complex chain of reactions. In this work, we simulate ab initio the X-ray absorption spectrum, Auger decay processes and the subsequent fragmentation dynamics of two hydride molecular ions, namely CH 2 + and CH 3 + . We show that these ions feature strong X-ray absorption resonances which relax through Auger decay within 7 fs. The doubly-charged ions thus formed mostly dissociate into smaller ionic carbon fragments: in the case of CH 2 + , the dominant products are either C + /H + /H or CH + /H + . For CH 3 + , the system breaks primary into CH 2 + and H + , which provides a new route to form CH 2 + near a X-ray source. Furthermore, our simulations provide the branching ratios of the final products formed after the X-ray absorption as well as their kinetic and internal energy distributions. Such data can be used in the chemistry models of the interstellar medium. Ultrafast electronic and nuclear dynamics induced by X-ray absorption in carbon hydride molecular ions are theoretically investigated.