[Todos] IAFE-COLOQUIO: " Molecular processes in interstellar clouds".]

[difusion en iafe.uba.ar]

               PRÓXIMO COLOQUIO DEL IAFE
            Instituto de Astronomía y Física del Espacio
                          CONICET-UBA
_________________________________________________________________________


               " Molecular processes in interstellar clouds".
                             Ronald McCarroll
  Laboratoire de Chimie Physique (UMR 7614 du CNRS), Université Pierre et
Marie Curie, Paris, Francia
                  Viernes 23 de noviembre 2012, 15:00hs.
                         Aula del Edificio IAFE


Interstellar space is filled with a very dilute gas in which new stars and
planets can form. Despite the exceedingly low temperatures and densities
of interstellar clouds, more than 150 different molecules have been
observed indicating a rich and interesting chemistry. The relative
abundance of these molecules is governed by the kinetics of the elementary
atomic and molecular processes. Both gas phase processes (ion-molecule
reactions, photodissociation, dissociative recombination, radiative
association,…) and the formation of molecules on the surfaces of icy
interstellar grains are of importance. But prior to 1990, the absence of
experimental measurements at low temperatures, there was little incentive
to develop theoretical models. Since then, the development of supersonic
jets have made it possible to study reactive systems in the laboratory at
temperatures as low as 10-20K. On the theoretical side, the development of
large scale quantum mechanical methods on some simple systems has led to
many quantitative results which clarify the main issues.

In this talk, I shall be concerned with some applications of the
statistical theory of chemical reactions, which was originally developed
by J.C. Light in 1967 and W.H Miller in 1970 but never hitherto applied at
low temperatures.
Some recent results on H+-H2, H+-D2, D+-HD, CH+-H, S-H2, N-OH will be
presented for which it is possible to make detailed comparisons either
with the best quantum calculations and/or with experiment. The validity of
the statistical model is shown to be very satisfactory.