Molecular cloud chemistry and the importance of dielectronic recombination Export

@article{citeulike:4169351, abstract = {Dielectronic recombination (DR) of singly charged ions is a reaction pathway that is commonly neglected in chemical models of molecular clouds. In this study we include state-of-the-art DR data for He+, C+, N+, O+, Na+, and Mg+ in chemical models used to simulate dense molecular clouds, protostars, and diffuse molecular clouds. We also update the radiative recombination (RR) rate coefficients for H+, He+, C+, N+, O+, Na+, and Mg+ to the current state-ofthe- art values. The new RR data has little effect on the models. However, the inclusion of DR results in significant differences in gas-grain models of dense, cold molecular clouds for the evolution of a number of surface and gas-phase species. We find differences of a factor of 2 in the abundance for 74 of the 655 species at times of 104–106 years in this model when we include DR. Of these 74 species, 16 have at least a factor of 10 difference in abundance. We find the largest differences for species formed on the surface of dust grains. These differences are due primarily to the addition of C+ DR, which increases the neutral C abundance, thereby enhancing the accretion of C onto dust. These results may be important for the warm-up phase of molecular clouds when surface species are desorbed into the gas phase. We also note that no reliable state-of-the-art RR or DR data exist for Si+, P+, S+, Cl+, and Fe+. Modern calculations for these ions are needed to better constrain molecular cloud models.}, author = {Bryans, P. and Kreckel, H. and Roueff, E. and Wakelam, V. and Savin, D. W.}, citeulike-article-id = {4169351}, citeulike-linkout-0 = {http://arxiv.org/PS_cache/arxiv/pdf/0809/0809.4504v1.pdf}, keywords = {astrochemistry, atomic, data, ism, processes}, posted-at = {2009-03-12 20:39:43}, priority = {2}, title = {Molecular cloud chemistry and the importance of dielectronic recombination}, url = {http://arxiv.org/PS_cache/arxiv/pdf/0809/0809.4504v1.pdf}, year = {2008} }

TY - JOUR ID - citeulike:4169351 L3 - citeulike-article-id:4169351 N2 - Dielectronic recombination (DR) of singly charged ions is a reaction pathway that is commonly neglected in chemical models of molecular clouds. In this study we include state-of-the-art DR data for He+, C+, N+, O+, Na+, and Mg+ in chemical models used to simulate dense molecular clouds, protostars, and diffuse molecular clouds. We also update the radiative recombination (RR) rate coefficients for H+, He+, C+, N+, O+, Na+, and Mg+ to the current state-ofthe- art values. The new RR data has little effect on the models. However, the inclusion of DR results in significant differences in gas-grain models of dense, cold molecular clouds for the evolution of a number of surface and gas-phase species. We find differences of a factor of 2 in the abundance for 74 of the 655 species at times of 104–106 years in this model when we include DR. Of these 74 species, 16 have at least a factor of 10 difference in abundance. We find the largest differences for species formed on the surface of dust grains. These differences are due primarily to the addition of C+ DR, which increases the neutral C abundance, thereby enhancing the accretion of C onto dust. These results may be important for the warm-up phase of molecular clouds when surface species are desorbed into the gas phase. We also note that no reliable state-of-the-art RR or DR data exist for Si+, P+, S+, Cl+, and Fe+. Modern calculations for these ions are needed to better constrain molecular cloud models. TI - Molecular cloud chemistry and the importance of dielectronic recombination KW - astrochemistry KW - atomic KW - data KW - ism KW - processes AU - Bryans, P AU - Kreckel, H AU - Roueff, E AU - Wakelam, V AU - Savin, DW PY - 2008/// UR - http://arxiv.org/PS_cache/arxiv/pdf/0809/0809.4504v1.pdf ER -