Abstract
Long-range intermolecular forces play a crucial role in controlling the outcome of ion–molecule chemical reactions, such as those determining the disappearance of organic or inorganic “complex” molecules recently detected in various regions of the interstellar medium due to collisions with abundant interstellar atomic ions (e.g. H+ and He+). Theoretical treatments, for example, based on simple capture models, are nowadays often adopted to evaluate the collision-energy dependence of reactive cross sections and the temperature dependent rate coefficients of many ion–molecule reactions. The obtained results are widely used for the modelling of phenomena occurring in different natural environments or technological applications such as astrophysical and laboratory plasmas. Herein it is demonstrated, through a combined experimental and theoretical investigation on a prototype ion–molecule reaction (He++methyl formate), that the dynamics, investigated in detail, shows some intriguing features that can lead to rate coefficients at odds with the expectations (e.g. Arrhenius versus anti-Arrhenius behaviour). Therefore, this study casts light on some new and general guidelines to be properly taken into account for a suitable evaluation of rate coefficients of ion–molecule reactions.
Original language | English |
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Pages (from-to) | 51-59 |
Number of pages | 9 |
Journal | ChemPhysChem |
Volume | 19 |
Issue number | 1 |
DOIs | |
Publication status | Published - 5 Jan 2018 |
Externally published | Yes |
Funding
The authors thank the COST Action CM1401(Our Astrochemical History) for support. F.P. acknowledges funding from MIUR (PRIN 2015, STARS in the CAOS—Simulation Tools for Astrochemical Reactivity and Spectroscopy in the Cyberinfrastructure for Astro-chemical Organic Species, 2015F59J3R). P. T. and D.A. acknowledge support from the Department of Physics of the University of Trento. The authors are grateful to Andrea Maranzana from the University of Turin (Italy) for support with CPU time at Turin University.
Keywords
- astrochemistry
- charge transfer
- ion–molecule reactions
- mass spectrometry
- reaction mechanisms