NDLI: Refit to numerically problematic UMIST reaction rate coefficients

Content Provider	EDP Sciences
Author	M. Röllig
Abstract	Aims. Chemical databases such as the UMIST Database for Astrochemistry (UDFA) are indispensable in the numerical modeling of astrochemical networks. Several of the listed reactions in the UDFA have properties that are problematic in numerical computations: some are parametrized in a way that leads to extremely divergent behavior for low kinetic temperatures. Other reactions possess multiple entries that are each valid in a different temperature regime, but have no smooth transition when switching from one to another. Numerically, this introduces many difficulties. We present corrected parametrizations for these sets of reactions in the UDFA06 database.Methods. From the tabulated parametrization in UDFA, we created artificial data points and used a Levenberg-Marquardt algorithm to find a set of improved fit parameters without divergent behavior for low temperatures. For reactions with multiple entries in the database that each possess a different temperature regime, we present one joint parametrization that is designed to be valid over the whole cumulative temperature range of all individual reactions.Results. We show that it is possible to parametrize numerically problematic reactions from UDFA in a form that avoids low temperature divergence. Additionally, we demonstrate that it is possible to give a collective parametrization for reaction rate coefficients of reactions with multiple entries in UDFA. We present these new fitted values in tabulated form.
Page Count	11
File Format	HTM / HTML PDF
ISSN	00046361
Alternate Webpage(s)	https://www.aanda.org/articles/aa/abs/2011/06/aa14743-10/aa14743-10.html
e-ISSN	14320746
Journal	Astronomy & Astrophysics
Volume Number	530
DOI	10.1051/0004-6361/201014743
Language	English
Publisher	EDP Sciences
Publisher Date	2011-06-01
Access Restriction	Open
Rights Holder	© ESO, 2011
Subject Keyword	astrochemistry astronomical databases: miscellaneous methods: numerical ISM: general astrochemistry / astronomical databases: miscellaneous / methods: numerical / ISM: general
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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