date: 2011 November 16 (Wed) 15:00-15:45
room: CPS Conference Room
speaker: Valentine Wakelam (Laboratory of Astrophysics of Bordeaux / University of Bordeaux)
organizer: Yuri Aikawa
title: Improving the quality of chemical model predictions for the interstellar medium
abstract: The observation of molecules in the interstellar medium (ISM) gives information on the physic of the formation of stars and planets. Dense clouds show large abundances of unsaturated species formed in cold gas phase whereas in protostars, gas warm up favors grain surface reactions and the formation of large saturated molecules. With the improvement of observational instrument sensitivity and the opening of new wavelength ranges, more and more trace molecules are detected in the ISM. The future far-infrared space telescope Herschel and (sub) millimeter interferometer ALMA are promises of opening new windows on the ISM wealth. The more molecules are discovered, the more complex chemical models have to be to reproduce this peculiar chemistry.
Any improvement of the treatment of the physics and dynamic in chemical models is pointless if the chemistry is wrong. Current chemical networks contain more than 4000 reactions. In addition to the fact that these networks are probably incomplete for the most complex molecules, only a small percentage of them have been studied in the ISM temperature range (between 10 and 300 K). The accuracy of chemical models relies on reaction rate coefficients computed and measured by chemists and physicists. Studying a reaction in detail can take years. For this reason, sensitivity analysis have to be conducted to guide experimentalists and theorists on the most important reactions to be studied to improve chemical models. I will present in this talk the methods we have developed to improve the quantitative aspects of chemical model predictions and the set up of a new public kinetic database for astrochemistry (KIDA