New extended deuterium fractionation model: assessment at dense ISM conditions and sensitivity analysis

Observations of deuterated species are useful in probing the temperature, ionization level, evolutionary stage, chemistry, and thermal history of astrophysical environments. The analysis of data from ALMA and other new telescopes requires an elaborate model of deuterium fractionation. This paper presents a publicly available chemical network with multi-deuterated species and an extended, up-to-date set of gas-phase and surface reactions. To test this network, we simulate deuterium fractionation in diverse interstellar sources. Two cases of initial abundances are considered: i) atomic except for H2 and HD, and ii) molecular from a prestellar core. We reproduce the observed D/H ratios of many deuterated molecules, and sort the species according to their sensitivity to temperature gradients and initial abundances. We find that many multiply-deuterated species produced at 10 K retain enhanced D/H ratios at temperatures \la 100 K. We study how recent updates to reaction rates affect calculated D/H ratios, and perform a detailed sensitivity analysis of the uncertainties of the gas-phase reaction rates in the network. We find that uncertainties are generally lower in dark cloud environments than in warm IRDCs and that uncertainties increase with the size of the molecule and number of D-atoms. A set of the most problematic reactions is presented. We list potentially observable deuterated species predicted to be abundant in low- and high-mass star-formation regions.Comment: 30 pages, 8 figures, accepted for publication in ApJ

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

Dissociative recombination

International audienceExperimental and theoretical developments in the field of dissociative recombination research over the last 15 years are reviewed. Rate coefficients and branching ratios for final channels of the reaction are tabulated

Demonstration of soot Particle Resizing in an Ethylene Flame by Small Angle X-Ray Scattering

International audienceThe size distribution of soot nanoparticles in an ethylene flame has been mapped in an in situ small angle x-ray scattering measurement at the European Synchrotron Radiation Facility. It has been seen that an abrupt size distribution change occurs at about a third of the flame's visible height and this is believed to be due to the oxidation and dehydrogenation of the particles

The dissociative recombination of fluorocarbon ions III: CF+2 and CF+3

International audienceCross sections and branching ratios are presented for the dissociative recombination of the CF+2 and CF+3 ions with electrons. It is found that the channel producing CF + F is dominant for the reaction with CF+2 and the production of CF2 + F is dominant for the reaction with CF+3. The cross sections for these two ions are very similar